On an October morning four years ago, eight young staff members at the Indiana Voter Registration Project in Indianapolis were planning their final steps before a closely contested presidential election. In recent weeks they had registered 45,000 new voters, most of whom were Black and Latino, and they were on track to enlist 10,000 more before Election Day. Their work had gone smoothly for the most part, but several canvassers had submitted applications with names that appeared to have been made up or drawn from the phone book, most likely to create the appearance that they were doing more work than they had actually done. That was illegal — submitting a false registration is a felony under Indiana law — and also frustrating. A made-up name was not going to help anyone vote. The staff members stopped using the suspect canvassers, but they couldn’t simply trash the faulty registrations: State law required them to file every application they collected, even if they had false names or serious mistakes. So they carefully identified all the applications with potentially false names, along with several hundred more with incorrect addresses or other simple errors, so that local election clerks would know they might present a problem.

Despite their efforts at transparency, though, Indiana’s secretary of state, Connie Lawson, used these faulty registrations as evidence of wrongdoing. She warned all the state’s county elections clerks that a group of “nefarious actors” who were going “by the name of the Indiana Voter Registration Project” had “forged voter registrations.” It was a gross exaggeration, but the project hired a lawyer to visit local election board offices and assure registrars that they were following the proper procedures. Craig Varoga, a longtime Democratic operative who runs Patriot Majority USA, which funded the Indiana project, told reporters that the fraud claims were false. Lawson was a close ally of Mike Pence, the state’s former governor who was then Donald Trump’s running mate. “We believe she is using government resources,” Varoga said, “to discredit and impugn the entire process.”

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But the staff members did not expect anything like what came that October morning. Around 10:45, five unmarked state police cars and a mobile cybercrimes unit quietly approached their building. A staff member heard a knock on the back door. Within minutes, troopers were rounding up the staff members inside the office, announcing that they had a warrant to search all their computers, cellphones and records. When one staff member, a young Black man, refused to give up his phone, the troopers handcuffed him — for “acting like a hoodlum,” he later said in a sworn affidavit. Within a couple of hours, the police were heading out the door with computers and phones as a television news crew captured the scene.

Pence seized on the investigation in interviews. “Voter fraud, Dana, is real,” he told the CNN correspondent Dana Bash. “We’re dealing with it in the state of Indiana right now. We have literally thousands of instances of fraudulent voter registration.” This claim was a misrepresentation, but it was of a piece with similar claims circulating around the country. The Pennsylvania State Police raided a Democratic firm that it said was suspected of producing fraudulent registrations. Conservative activists released a report titled “Alien Invasion in Virginia,” claiming that more than a thousand “noncitizens” there were poised to vote illegally. A video from Project Veritas’s right-wing video ambush artist James O’Keefe III caught a Democratic operative seemingly discussing a hypothetical “huge, massive voter-fraud scheme” in Wisconsin, as Sean Hannity described it. Some of the claims were simply nonsensical. Roger Stone, Trump’s longtime adviser, tweeted a fictitious document that purported to reveal a Democratic plan to attack American voters with mind-controlling “pulsed ELF electromagnetic emissions” and impose martial law, adding only, “If this is real: OMG!!!”

[Read the main takeaways from this investigation.]

None of these stories held up under examination: The Pennsylvania authorities never followed the raid with a case; there were no official findings of illegal voting by noncitizens in Virginia; a Wisconsin attorney general’s investigation failed to uncover a “massive voter-fraud scheme.” In Indiana, a judge dismissed charges against a manager at the Indiana Voter Registration Project, and prosecutors dropped the cases against nine of its former canvassers after they agreed to pay fines and confirm as true the charges against them. Two of the former canvassers did plead guilty to making false statements on government forms and received sentences of community service and probation.

But all those headlines about voter fraud — amplified daily on Facebook and Twitter — served a purpose: They laid the groundwork for a legal challenge. The Trump campaign had a team of election lawyers standing by to dispute election results throughout the country, and the Republican National Lawyers Association had readied a self-described “Navy SEAL-type” operation to fight similar cases. In the event of a Republican loss, they would need a story, and fraud was it. The truth appeared to be a secondary concern at best.

Victory did little to change their stance. Shortly after his inauguration, President Trump told a bipartisan group of senators that his narrow loss in New Hampshire was due to voter fraud. Thousands of out-of-state voters apparently voted illegally, he said, after they were bused in to New Hampshire from Massachusetts. After Trump’s rant was leaked to reporters, the ABC anchor George Stephanopoulos asked the senior presidential adviser Stephen Miller if he really believed that to be the case. The practice of busing in illegal, out-of-state voters was “widely known” in New Hampshire, he said. But he declined to provide evidence, adding that “voter fraud is something we’re going to be looking at very seriously.”

As the 2020 presidential election nears, it is becoming clear that the Trump administration and the Republican Party are not just looking at but heavily investing in the largely nonexistent problem of voter fraud. A New York Times Magazine investigation, based on a review of thousands of pages of court records and interviews with more than 100 key players — lawyers, activists and current and former government officials — found an extensive effort to gain partisan advantage by aggressively promoting the false claim that voter fraud is a pervasive problem. The effort takes its most prominent form in the president’s own public statements, which relentlessly promote the false notion that voter fraud is rampant.

This story did not originate with Trump. It has its roots in Reconstruction-era efforts to suppress the votes of newly freed slaves and came roaring back to life after the passage of the Voting Rights Act. But it is reaching an apex now, as a president who lost the popular vote in 2016 and is currently trailing in the polls harnesses the reality-warping powers of social media and the resources of at least four federal agencies to undermine faith in an election he could very well lose.

Voter fraud is an adaptable fiction, and the president has tailored it to the moment. Even as the coronavirus pandemic poses a grave obstacle to his re-election, the crisis is providing him an opportunity to do what no other president has done before him: use the full force of the federal government to attack the democratic process, suppress the votes of American citizens and spread grievance and suspicion among his followers. Recently, perhaps predictably, the president has begun to suggest that because of his professed distrust in the election process, he will not agree to a peaceful transition of power.

It is remarkable, but not at all accidental, that a narrative built from minor incidents, gross exaggeration and outright fabrication is now at the center of the effort to re-elect the president. As we approach an election in which the threat of voter fraud is being used as a justification for unprecedented legal and political interventions in our democratic process, it is important to understand what this claim actually represents: It is nothing short of a decades-long disinformation campaign — sloppy, cynical and brazen, but often quite effective — carried out by a consistent cast of characters with a consistent story line. Even the Indiana Voter Registration Project remains in play. “In my own state of Indiana in 2012,” Pence said on Fox News in July, “literally, there was a group of people that were prosecuted for falsifying ballots.” He had the year wrong and the facts wrong. But the Indiana case was nevertheless proof, he said, that “the reality of voter fraud is undeniable.”

The modern era of voter-fraud claims began on a November morning in 2000, inside a drab office building in downtown Miami — home of the Miami-Dade County election supervisor. Al Gore was contesting the results of the Florida presidential vote count, which showed a very small margin in favor of George W. Bush. Up against a court-imposed deadline, the Miami-Dade canvassing board voted to recount 10,750 ballots that had been rejected by its electronic machines, letting the 643,250 others stand, a decision that, at the time, seemed as though it could tip the vote to Gore.

With a Republican protest growing inside and around the building, the election board had moved its counting to a room on the 19th floor, away from the crowd. Stone, who helped guide Trump’s first, short-lived bid for the presidency during the 2000 primaries, has proudly promoted himself as an organizer of the demonstration, which involved several young white male rising stars of the conservative-operative ranks. The group stormed the counting room in a crashing human wave of clenched fists, pleated khakis and button-down shirt collars. Banging on doors and walls, they chanted, “Stop the fraud!”

The effort was obviously in bad faith — reporters called it the Blue Blazer Riot, the Bourgeois Riot and the Brooks Brothers Riot — but the board was sufficiently intimidated. It suspended the count less than a quarter of the way through, when it had shown a net gain of nearly 160 votes for Gore. It would never resume. If the rest of the ballots had broken the same way, Gore would have gained more votes than Bush’s final winning margin in Florida of 537. The success of the Brooks Brothers Riot confirmed that a fraud claim — even an unconvincing one — could help determine a chaotic, contested election.

The incident heralded a new approach to an old technique. Powerful Americans have long deployed the claim of fraud to disenfranchise powerless Americans. White-supremacist poll watchers emerged in the Reconstruction era, along with poll taxes designed to prevent supposed repeat voting and other methods to suppress Black voters. The Voting Rights Act of 1965, the crowning achievement of the civil rights movement, did away with these “tests or devices,” as it called them, but its passage also set in motion a historic realignment of the parties, largely along racial lines. The Republican Party became increasingly white, even as white Americans represented a shrinking portion of the electorate.

After the messy outcome in Florida, the Bush administration quickly moved to embrace the new cause of what his administration called “election integrity.” The Justice Department’s civil rights division, established by the Civil Rights Act of 1957, had long worked to protect Black and Latino citizens from intimidation at the polls. Now, though, it would begin working toward what conservative legal thinkers were calling “colorblind” enforcement, recruiting a new generation of right-leaning lawyers with hard-edged views about voter fraud and the need to protect against it. They included the lawyer J. Christian Adams — who would go on to co-publish the 2016 “Alien Invasion in Virginia” report through his Indianapolis-based Public Interest Legal Foundation, or PILF — and Hans von Spakovsky, a Georgia elections official and PILF board member who was also on the scene as a Bush recount observer in Florida.

The new team made history by bringing a successful Voting Rights Act case on behalf of white citizens in Mississippi, claiming that the Black leadership of a majority Black county had employed illegal voting schemes to dilute the votes of the white minority. When career voting rights lawyers at the department recommended blocking a new voter-identification law in Georgia — on the grounds that the law threatened to disproportionately restrict the voting rights of poorer citizens, who were also disproportionately Black and Hispanic — von Spakovsky and like-minded officials overruled them. (A judge later ruled that the law was discriminatory.)

But the voter-fraud effort was not limited to the civil rights division. When Attorney General John Ashcroft pushed United States attorneys to bring more voter-fraud cases, prosecutors struggled to find deliberate schemes, in many cases sweeping up people who made mistakes on forms or misunderstood eligibility rules. And congressional and inspector-general investigations later unearthed documents revealing that the Bush Justice Department, in consultation with the White House, had abruptly fired multiple United States attorneys after they refused to accede to pressure to hew to partisan political considerations, including, in three instances, declining to bring voter-fraud-related cases.

In October 2008, as another presidential election neared, several F.B.I. field offices began investigating the Association of Community Organizations for Reform Now, or ACORN, which, among other community services, was then engaged in one of the largest national voter-registration drives in the country. The group, which mostly served poor neighborhoods, many of them nonwhite, had tenuous ties to Barack Obama, who was one of three attorneys who represented it in a 1995 voting rights suit. Like the Indiana authorities in 2016, the F.B.I. was investigating canvassers who provided fraudulent registrations, in this case to ACORN. And like Mike Pence in 2016, John McCain, the Republican presidential candidate, took the opportunity to portray voting rights activists not as the victims of a minor fraud but as the perpetrators of a major one, asserting that ACORN was on the verge of “destroying the fabric of democracy.”

The F.B.I. investigations led to no major federal indictments, but among some conservatives, “ACORN” quickly became the one-word explanation for nefarious forces that propelled a Black man to the presidency. O’Keefe reinforced the narrative when he released videos purporting to show ACORN staff members offering advice to O’Keefe, who presented himself as a pimp seeking advice on how to secure a loan for a brothel, the profits from which he could use to fund a political campaign. The highly edited videos offered no evidence of illegality, but the scandal on top of the investigation ultimately forced ACORN out of existence.

Even as McCain lost the race, the ACORN “scandals” helped usher in the largest curtailment of voting rights since the 1960s. As the reactionary Tea Party wave swept Republicans into statehouses, restrictive new laws took hold across the country, all in the name of combating “fraud.” Many states rolled back early voting, which had been vital to successful “Souls to the Polls” efforts by Black churches. Kansas and other states passed restrictive new voter-ID or “proof of citizenship” laws, whose new burdens fell harder on nonwhite voters, who were statistically less likely than white voters to have the necessary paperwork. Those laws came even faster after 2013, when the Supreme Court, led by Chief Justice John G. Roberts Jr., a Bush appointee, gutted the most powerful enforcement mechanism of the Voting Rights Act. “Our country has changed,” Roberts concluded in his opinion for the majority, “and while any racial discrimination in voting is too much, Congress must ensure that the legislation it passes to remedy that problem speaks to current conditions.”

Trump filed his paperwork for the 2020 election on the day he was inaugurated, and within weeks he started an effort that would be central to the campaign: forming his Presidential Advisory Commission on Election Integrity. The purpose of the commission, as Trump explained on Twitter, would be to collect evidence of the widespread voter fraud that had robbed him of a popular-vote win and suggest actions that he could take as president to prevent it from happening again.

Pence would be its chairman, but the real work would fall to its vice chairman, Kris Kobach. As the Kansas secretary of state, Kobach had created some of the harsher immigration and election policies enacted during the Obama years, including proof-of-citizenship requirements for voter registration. Kobach had his eyes on higher office, but a shot at the No. 2 spot in Trump’s Homeland Security Department was blocked by its new head, John Kelly. Now he had found a home.

The right staffing would be essential to success. Pence had assigned two senior aides to help Kobach run the commission, Andrew Kossack and Mark Paoletta. Kossack, who would be the commission’s executive director, had been Pence’s revenue commissioner in Indiana and knew his way around bureaucracy. Paoletta, Pence’s chief counsel, was a conservative legal ace who had served with distinction in Republican political and congressional theaters: He helped run the opposition-research effort against Anita Hill during the Senate confirmation hearings of Justice Clarence Thomas; was part of the war room that the McCain campaign set up to defend Sarah Palin in 2008; and led the investigative team of the House Committee on Energy and Commerce during the Enron and Martha Stewart investigations.

They quickly engaged with the two leading proponents of the voter-fraud narrative, the former Bush Justice Department lawyers Adams and von Spakovsky, who would advise on research and personnel. The commission needed commissioners, of course, and the team initially picked three conservative veterans of the partisan voting wars. The first was Lawson, the Indiana secretary of state. The second was Christy McCormick, a Bush-era Justice Department lawyer who was then a Republican member of the Election Assistance Commission, the federal agency responsible for distributing federal election money to states and setting national guidelines on security and registration standards. She had made her bones with Trump by publicly questioning the intelligence reports on Russian election interference while speaking out against the Obama administration’s post-election steps to secure the national voting infrastructure. Rounding out the initial three Republican board members was Ken Blackwell, a former Ohio secretary of state whose partisan approach to voting rules during the 2004 presidential election was widely credited with delivering the state to George W. Bush.

To satisfy a tradition of balanced presidential commissions, they would also need some Democrats. For von Spakovsky, this was a concern from the start. “There isn’t a single Democratic official that will do anything other than obstruct any investigation of voter fraud,” he warned in an email. But the commission leaders found two safe-seeming bets: Bill Gardner, who as New Hampshire’s secretary of state had supported stricter voter-ID laws, and Matthew Dunlap, who as Maine’s secretary of state had bonded with Kobach at national conventions. “We’d sit at dinner, and we’d talk about various loads of the thirty-aught-six — which is best for elk, which is best for moose,” Dunlap told me this summer.

Over time, Dunlap came to believe that either he was being used as a figurehead or the commission wasn’t doing anything, because he heard little else after he was named. But behind the scenes, von Spakovsky, Adams, Kobach and the vice president’s aides were in regular contact and were soon planning a public meeting to showcase the latest research on voter fraud. All the commissioners would be present at the meeting, which was set to take place in New Hampshire that September.

Among the findings was a report from the Government Accountability Institute — a conservative think tank founded by Stephen K. Bannon, Trump’s former campaign chief, and the conservative writer and political consultant Peter Schweizer. Much of the funding for the institute came from Robert and Rebekah Mercer, the billionaire political activists who had also backed Bannon’s website, Breitbart News. Schweizer introduced Paoletta to the report’s author, and Paoletta helped arrange his testimony, internal commission emails showed. (Schweizer and Paoletta had other common concerns. It was Schweizer who would go on to write a book raising questions about Joe Biden’s son Hunter and his actions in Ukraine; it was Paoletta who would help devise the Trump administration’s legal rationale for withholding congressionally approved aid from Ukraine as Trump pressured its new government to investigate the Bidens. Through a spokeswoman, Paoletta said he had not maintained contact with Schweizer after his work on the commission.)

A central claim of the report was that some 8,500 people voted twice in 2016. The evidence was shaky, though — one prominent political scientist, Paul Gronke of Reed College, called the research “sloppy and misinformed.” But days before the meeting, Pence’s office came across information that could make for a blockbuster announcement, giving Trump exactly what he was looking for: An analysis of voter rolls by the New Hampshire secretary of state’s office found that 6,540 people who had registered to vote on the day of the 2016 election had presented out-of-state driver’s licenses, yet only 1,014 of them had switched their licenses over to New Hampshire in the months since. Kossack alerted Kobach and Paoletta in an email, suggesting that the rest appeared to be out-of-state residents who could have swung the election. Hours later, Kobach published a column on Breitbart’s website, declaring that, in all likelihood, the New Hampshire election “was stolen through voter fraud.”

When Gardner, New Hampshire’s secretary of state, heard Kobach’s description of the findings at the meeting, though, he immediately objected. The discrepancy could be explained by the simple fact that residents of other states are allowed to vote in New Hampshire if they are effectively living there, as thousands of out-of-state college students most certainly were. When Kobach asserted that perhaps the legitimacy of the election would never be known, Dunlap was incredulous. “Making this equation that somehow people not updating their driver’s license is an indicator of voter fraud would be almost as absurd as saying that if you have cash in your wallet, that’s proof that you robbed a bank,” he said, drawing laughter from the audience.

From that point on, Dunlap said, he was shut out. The commission had come to view him as “a saboteur,” as Adams put it to me, and Dunlap came to see Kobach and his cohort as “voter-fraud vampire hunters” who treated any rare example of actual fraud, no matter how accidental or inconsequential, as proof of its ubiquity. Stonewalled by the committee, Dunlap decided that he would need to take more extreme steps. That November, with the help of the nonpartisan watchdog group American Oversight, he sued his own commission, demanding that it share its records and stop excluding him from commission business. He would ultimately obtain 8,000 pages of pages of emails and plans and post them publicly on his Maine secretary of state website.

The documents showed that there was a much larger project in the works. In several meetings, Kobach, von Spakovsky, Adams, McCormick and the vice president’s office had discussed the creation of a gargantuan database of government-held information to search national voter rolls and find irregularities. Such list matching, as the practice is known, is the means by which states regularly analyze their voting rolls to ensure that they do not contain dead people or people who have moved out of state. But when data matching is done poorly, it can be a prolific source of false claims about supposedly invalid voters and can cause wrongful cancellations of large numbers of legitimately registered citizens. In the wrong hands, there could be no more powerful engine of voter suppression.

Kobach had built out a prototype for such a database as Kansas secretary of state. His Interstate Voter Registration Crosscheck system matched first and last names and birthdays of registered voters across nearly 30 states. But it had serious flaws. One study showed that Kobach’s program would cause 300 wrongful terminations for every double registration it might prevent; another study found that nonwhite voters — who are more likely to share the same names than white voters are — were far more likely to be flagged in its data. The entire program was ultimately suspended because of litigation.

Now the commission was planning a sprawling federal version of Kobach’s Crosscheck system. Its Republican members wanted access to government data from the Department of Education, the Internal Revenue Service, the Department of Homeland Security, Citizenship and Immigration Services, public-assistance services and the federal court system, as well as from all 50 states. All of it would feed into what was to be the mother of all voter-fraud reports. The premium data it was seeking to use could have helped lead to more accurate voting rolls, with hundreds of data scientists and a long period of study, Charles Stewart III, a political scientist at the Massachusetts Institute of Technology who provides expert analysis for voting rights cases, told me. But with the resources the commission had and the time frame on which it was working, he said, the final product promised to be “a total dumpster fire” of sensational charges based on flawed data matching. (A spokeswoman for Kobach said the commission would have handled voter data responsibly and that any match would have been “a starting point for additional investigation.”)

The Dunlap documents revealed a project with high hopes. Before any of this data had even arrived, the commission’s staff prepared a draft version of a report with a section titled: “Evidence of Election Integrity and Voter Fraud Issues.” There were subcategories labeled, with anticipation, “False registrations (deceased individuals, fictitious identities, etc.)” and “Noncitizen registration.” Blank spaces were left to be filled in later. The draft report also called for unspecified changes to be made to the Help America Vote and National Voter Registration Acts, the two most important federal laws since the Voting Rights Act, devised to further expand access to voting and enhance security measures. And it proposed unspecified new methods for “investigating and prosecuting election crimes.”

By January 2018, with Dunlap winning early decisions and with lawsuits over state data requests progressing, Trump made an abrupt announcement. “Rather than engage in endless legal battles at taxpayer expense,” he said, he would be shutting down the committee. But the larger project would live on elsewhere. The president had asked a different agency — the Department of Homeland Security — “to review these issues and determine next courses of action.”

Voter registration may have seemed like an odd fit for the Department of Homeland Security, but within days, the Kobach commission’s work had found an enthusiastic reception in the department’s border, immigration and trade policy office. The office had a hand in developing many of the nativist policies promoted by Trump’s lead immigration adviser, Stephen Miller: the president’s “big, beautiful wall,” family separation, “extreme vetting.” Now it would help lead the department onto new terrain.

The focus, according to emails produced in a public-records lawsuit filed by the Brennan Center for Justice at New York University with a legal group called Protect Democracy, would be on blocking another perceived threat from Latinos. Among those who picked up the remit, emails show, was a policy analyst named Ian M. Smith. In a column for The Daily Caller, Smith had described Hispanic immigration as a threat to “America’s historic character.” He had also been, according to a copy of his résumé obtained by American Oversight, an intern for Hans von Spakovsky at the Heritage Foundation, where he “drafted reports and memoranda on voting and election law.”

In a January email, Smith revealed that his team was working on ideas for a national voter-identification requirement as part of the project. At first glance, such a requirement might seem reasonable enough, but voter-ID requirements can be tailored to create disproportionate burdens on historically disenfranchised groups. A 2018 survey by the Public Religion Research Institute and The Atlantic found that Black and Hispanic people were three times as likely as white people to say that they had been told at polling stations that they lacked the proper identification. Even when Black citizens do have government-issued ID, states may deliberately reject it. In one version of its voter-ID law that was struck down in the courts in 2019, North Carolina had excluded from its list some forms of ID held disproportionately by Black residents, including all but a small number of government-employee cards.

Dunlap told me that, from the emails, Smith appeared to be working on the same “harebrained” proposal that had come up while he was on the commission, one that would require all voters to present “Real ID” cards in order to cast a ballot. Real ID cards, a Homeland Security Department innovation dating to 2005, will be required for entry at federal facilities and to board commercial flights starting late next year. In order to obtain one, people must present an array of documents proving their citizenship. Requiring such a test in order to vote, Dunlap said, “would be a game changer.”

Smith, whose involvement in the voting project has not been previously reported, would not last long enough at the department to see it through. The department forced him to resign later that year, after The Atlantic obtained several emails revealing his friendly interactions with prominent white nationalists and neo-Nazis and his acceptance of an invitation to a “Judenfrei” (Jewish-free) dinner. (Smith declined to comment in detail about his resignation or his work on the project.)

The department emails also give a hint of an even more ambitious plan to expand Kobach’s crosschecking. Several exchanges involved questions about the department’s position on providing state election officials with access to its Systematic Alien Verification for Entitlements, or SAVE, database, which tracks the status of immigrants. After Florida sued for access to the database in 2012, the Obama administration agreed to share the data with states on a limited basis. Now Republican state officials were clamoring for more extensive access to identify undocumented immigrants who were supposedly illegally registered on voter rolls. Its potential utility had been mentioned in internal communications of the Kobach commission. Heavily redacted emails from January and February 2018 appear to show Department of Homeland Security officials discussing whether the department had legal clearance to grant it. A message from an official with its civil rights division urged safeguards for those “who could be disenfranchised based on erroneous determinations.”

Adams, for his part, was about to discover the consequences of bad data. In April 2018, the League of United Latin American Citizens filed suit against Adams’s group on behalf of several Virginians who accused PILF of defaming them in its 2016 “Alien Invasion in Virginia” report or its 2017 sequel, “Alien Invasion II.” PILF and a related group called the Virginia Voters Alliance had identified them as being among thousands of “noncitizens” who had registered to vote in Virginia and, in many cases, did vote, committing “felonies upon felonies.” The plaintiffs, however, were American citizens.

The reports were based in part on lists of people that local election officials had removed from voting rolls because they had indicated on driver’s-license renewal forms or other state records that they were not citizens. Emails released in the discovery process show that one election official had warned PILF that such lists could be unreliable: Actual citizens appeared to sometimes answer questions about their citizenship on renewal and application forms incorrectly. In another email, an associate said that he had found some specific cases in which a supposed noncitizen did seem to be a citizen.

But Adams and others on the project weren’t concerned. In one email, the PILF spokesman Logan Churchwell wrote that even if the lists turned out to be inaccurate, it would create even more questions about how Virginia was handling its voter rolls. “We still have the opportunity to convert pushback into official confusion to justify our call for top-down overhaul,” Churchwell wrote to Adams. “The fog of war favors the aggressor here.” Discussing the second report on Tucker Carlson’s show on Fox News in 2017, Adams said, “This is the real foreign influence in American elections.” In a settlement in July of last year, PILF agreed to apologize and strike exhibits featuring the names of people who were in fact citizens and did not commit felonies.

In late August, Adams told me that PILF deserved credit for showing that Virginia was removing voters from rolls based on flawed conclusions about their citizenship. In Adams’s view, liberal bias was causing reporters to overlook serious problems in state registration lists that groups like his were identifying. “This is all in earnest,” he said. “We’re not doing this because we’re trying to help somebody win an election. The stuff we’re finding ought to concern everybody.”

Yet the sensationalistic particulars of voter fraud that were thriving online and on Fox News were withering in the evidentiary fluorescence of the courts. In Kansas, a federal judge struck down Kobach’s proof-of-citizenship law, ruling that “the magnitude of potentially disenfranchised voters” could not be “justified by the scant evidence of noncitizen voter fraud.” (She also questioned the value of one of his expert witnesses, von Spakovsky, citing his “misleading evidence” that was “largely based on his preconceived beliefs about this issue.”) A federal judge decided against the plaintiffs in a suit that Adams helped bring to compel Broward County to winnow its rolls more aggressively, saying the argument relied in part on a “misleading” analysis.

The 2018 midterm elections did see one bona fide large-scale ballot-fraud effort. A political operative in North Carolina ran a complicated scheme in which he requested hundreds of ballots on behalf of unwitting voters and then intercepted them and filled them out for the candidate he was working for: the Republican congressional candidate Mark Harris. Election officials spotted the suspicious activity shortly after the vote, refused to certify the results and conducted a new election. Trump never posted on Twitter about this rare actual instance of fraud.

The North Carolina case had nothing to do with “ghost voters” or “double voters” or undocumented immigrant voters. Yet the hunt to rid voting rolls of these supposed specters was increasingly becoming the primary focus of conservative efforts. Between Georgia, Ohio and Texas alone, at least 160,000 people had been wrongfully blocked, scheduled for removal or removed from voter-registration lists in 2018 and 2019. Those marked for ejection were disproportionately Black and Latino. The states said these were simple mistakes. But Nina Perales of the Mexican American Legal Defense and Educational Fund, which in 2019 sued to stop a Texas purge of purported noncitizens that ensnared 98,000 voters, saw something else at play: “They’re trying to freeze the electorate in place,” she told me, “by preventing new folks from getting on the voting rolls.”

The coronavirus introduced a menacing new element of disruption to the coming presidential election. This April, as shutdowns and fear of exposure meant that voting by mail would be used by more Americans than ever before, David C. Williams quietly stepped down from his seat on the board of governors of the United States Postal Service, where he had served for nearly two years after having spent the previous 13 years as the service’s well-regarded inspector general. A week later, the board announced its selection of a new postmaster general, Louis DeJoy.

The appointment was curiously timed. DeJoy’s predecessor, Megan Brennan, an Obama holdover who worked her way up from the letter-carrier ranks, had announced her resignation in October. The board had been using two separate search firms in its methodical approach to choosing her successor. DeJoy, the longtime chief executive of a major logistics company that held several Postal Service contracts, was not on either firm’s list. He did not go through the normal vetting process, Williams would later assert, citing that irregularity as one reason for his resignation, as well as his personal reservations about DeJoy’s qualifications. Yet DeJoy had a clear conflict of interest: He still held a major stake in the firm that had bought his company and employed him for several years, which itself still had Postal Service contracts and stood to gain from a privatization plan that Trump was promoting. (In a statement, the Postal Service said that the Postal Inspection Service conducted a background check of DeJoy after he was offered the position but before he started and that DeJoy has recused himself from all decisions involving his old firm.)

DeJoy’s recommendation originated with the chairman, Robert M. Duncan. Duncan and DeJoy hailed from the same world of high-dollar Republicanism, and a Postal Service spokesman said they knew each other socially. Duncan is on the board of the Senate Leadership Fund, a super PAC linked to Mitch McConnell, the Senate majority leader; as the Republican National Committee chairman in 2008, he echoed the McCain campaign, warning that Democrats would benefit from “voters that do not exist.” DeJoy was a longtime Republican fund-raiser who had given lavishly to Republicans in recent years. An invitation for a big-donor event he held for Trump at his home had lamented “the extreme and unreasonable challenges” Trump faced, including from “federal employees,” The News & Observer of Raleigh had reported. The raw commingling of political interests was unusual for the Postal Service. But the service was entering unusually political territory.

Just a few weeks earlier, an election for the Wisconsin Supreme Court revealed the newly pivotal role that mail-in voting would play in American elections during a pandemic. The winner of the race would have influence over a suit to force a planned purge of 200,000 from voter rolls, which had been paused because of concerns about data errors.

With Covid-19 cases surging, Gov. Tony Evers, a Democrat, issued strict stay-at-home orders. By then, the Centers for Disease Control and Prevention had released urgent guidance directing election officials to move toward “voting methods that minimize direct contact with other people and reduce crowd size at polling stations.” The first of its specific recommendations: “Encourage mail-in methods of voting if allowed in the jurisdiction.”

Democrats quickly sued to suspend the state’s strict requirements that mail-in votes arrive by 8 p.m. on Election Day. They won an initial six-day extension for mail ballots, but in response to a late Republican appeal, the Supreme Court ruled on the election’s eve that no ballot would be counted that didn’t have a postmark from Election Day or earlier. In a smaller victory for Democrats, it let stand the order to extend the counting period.

Local data compiled over the following weeks showed that in several towns, the conservative incumbent won the in-person vote but the liberal challenger prevailed in the mail. Democratic officials said that at least 92,000 people who asked for ballots didn’t receive them in time to mail them back by Election Day. According to the Wisconsin Elections Commission, some 5,500 voters sent ballots that were postmarked after Election Day — too late to be counted under the Supreme Court’s new terms. At the same time, the extended counting deadline appeared to have saved nearly 80,000 people whose ballots had arrived after Election Day from disenfranchisement.

Here was a test that made one thing clear: For mail voting to work, time was an important X factor. Voters needed time to obtain and send ballots, the Postal Service needed time to deliver them and election officials needed time to count them. And more of them were likely to be Democrats. There were variables that Trump could control, in no small part through the Post Office.

With that realization, questions about DeJoy’s hiring began to take on added urgency, and Senator Chuck Schumer drafted a letter to Duncan, requesting a full and extensive accounting of DeJoy’s selection and any possible hand the White House might have had in it. He promptly received a letter from the Postal Service’s board secretary, Michael Elston, denying his request for information. (A White House official, who would speak only on the condition of anonymity, said the president was not directing internal decisions at the Postal Service.)

As it happened, Schumer had bumped up against Elston before, when Schumer helped lead the investigation into the Bush administration’s politically motivated firings of the United States attorneys. Elston was a senior Justice Department political appointee at the time and resigned under pressure. A later internal investigation determined that he had consulted on the firing plans and was “close to the line” of intimidation in his apparent efforts to keep the fired attorneys from speaking out. One witness in another investigation, this one in the Senate, also connected him to a questionably timed voter-fraud case against four workers for ACORN during the 2006 midterm elections. During the Trump era, Elston was elevated to board secretary, which meant he helped handle the logistics of DeJoy’s nomination. (After DeJoy’s nomination, Duncan assigned Elston to the postmaster general’s office to serve as an adviser, a Postal Service spokesman said, adding that he would have no role in mail operations.) About a week after DeJoy’s appointment, the Postal Service announced that another senior official was resigning, the deputy postmaster general, Ronald Stroman. Adams tweeted, “Good news from the #swamp: Ronald Stroman — deputy postmaster general who was working at cross purposes with @realDonaldTrump on #VoteByMail got booted, the hard way.”

Stroman told me that he wasn’t pushed out. “My leaving had more to do with the independence of the Postal Service,” he said. He said he had also developed a more fundamental disagreement with the Trump administration’s approach to the department over all, which included a proposed privatization scheme. Before he left, Stroman had been implementing a yearslong plan to improve the mail balloting system. As the coronavirus began its rapid spread, he came to realize that his plan was “nowhere near sufficient, given the volume we’re going to see, and you have states that just do not have the infrastructure or history of dealing with significant numbers of absentee ballots.” He was confident that they could get up to speed for November, but the Postal Service was going to have to continue to prioritize the work under its new management, and states were going to need far more resources to build out their vote-by-mail capabilities.

The $2 trillion Cares Act emergency-funding bill passed in March included $400 million for elections. Democrats had proposed federal requirements for states to effectively make mail-in ballots available to all voters for any reason and the extension of early voting, something closer to the $4 billion experts believed was necessary. Republicans, citing their opposition to federal mandates, treated those provisions as nonstarters. In the divisive Trump era, the $400 million was a result of a rare moment of shared purpose, and Senator Amy Klobuchar of Minnesota, the senior Democrat on the Rules Committee, which is responsible for the election money, had reason to be optimistic that Republicans would release more money in future relief bills. For one thing, she told me in July, the Rules Committee’s Republican chairman, Senator Roy Blunt of Missouri, had said publicly that he would work to get more money to states, and that as a former secretary of state, he understood the need.

Klobuchar had important allies on the Republican side in secretaries of state like Kimberly Wyman of Washington, who oversees one of the nation’s only vote-by-mail election systems. In Wyman’s determination, $400 million was a fair start, but it was woefully insufficient on its own.

“It’s not even knocking on the door of what these states are going to need,” Wyman told me. More money was vital to securing the most important element in achieving a clear-cut election outcome: the speed with which it can be determined. The longer a result remains in doubt, the more time there is to question the legitimacy of the entire election.

States that did not have all-mail elections — all but five — simply didn’t have the equipment necessary to quickly count the number of mail ballots they were going to be receiving. They required more high-speed sorters and envelope splicers and printers.

But as June became July and July became August, there was no sign that Senate Republicans would agree to release more money. A senior Democratic staff member with knowledge of the negotiations lamented to me that Republicans were opposing more financing with claims that fraudsters were going to show up at election offices with “bags of ballots.” The staff member, speaking on condition of anonymity, told me, “They’re starting to churn the Republican misinformation machine — that it lends itself to fraud, and it’s just not true.” It was beginning to dawn on Democrats that even if they did secure more money, it would have to pass through the Office of Management and Budget, which during Paoletta’s tenure had already set a precedent of holding back congressionally approved funds in the Ukraine scandal.

Republicans still had at least one compelling reason to more fully finance mail-in voting — the undeniable public-health imperative to switch to absentee balloting, recommended by the administration’s own top health agency. But quietly, in early summer, the C.D.C. changed its guidance on voting. Its elections web page no longer specifically mentioned mail-in voting as a safer alternative to in-person voting. The changes, which have not been previously reported, addressed mail ballots only in a brief section about possible dangers associated with them, suggesting that workers allow mail to sit for a few hours before handling it “to further reduce risk” and to carefully disinfect all machinery that comes into contact with it. Its final point: “Mail-in voting can make it more difficult for voters with disabilities to exercise their right to vote.” This was misleading. Mail voting is the primary means of voting for many people with disabilities. At that point, though, the White House was already moving to take over all government communications about the coronavirus.

Then came news that the new leadership at the Postal Service was cutting back on overtime and ending delivery shifts as scheduled, rather than when all the daily mail was delivered, leading to delays throughout the system. Union officials reported that sorting machines were being removed from post offices at unusual rates. Now the central mechanism of the vote-by-mail system was being badly hobbled — by executive action and congressional inaction. (A Postal Service spokesman said the cutbacks in overtime were part of a longstanding cost-saving effort.)

When Congress headed off for its summer recess with no deal on money for voting or the Postal Service, Trump told reporters. “They need that money in order to make the Post Office work, so it can take all of these millions and millions of ballots,” he said. “Now, if we don’t make a deal, that means they don’t get the money. That means they can’t have universal mail-in voting. They just can’t have it.” His Democratic opponent, Joe Biden, told CNN, “He doesn’t want an election.” Republicans played down Trump’s statements. And the Postal Service said sorting machines were removed only for lack of use; it said it was confident that it was prepared for the election. But Stanley Bastian, a federal judge in Washington, who would temporarily block DeJoy’s postal changes before the election, ruled, “At the heart of DeJoy’s and the Postal Service’s actions is voter disenfranchisement.”

Michigan, Pennsylvania and other states began pursuing ways to make up for the Postal Service delays and the lack of financing, easing deadlines and installing special ballot drop boxes throughout their counties. The Trump campaign, PILF and Judicial Watch filed or supported suits to block those moves. They cited one reason above others: fraud. “Defendants have sacrificed the sanctity of in-person voting at the altar of unmonitored mail-in voting,” a suit filed by the Trump campaign this June against counties in Pennsylvania read, “and have exponentially enhanced the threat that fraudulent or otherwise ineligible ballots will be cast and counted.”

The judge in that case was skeptical and demanded proof in August. The campaign struggled to provide any. But now it was primarily making its case on social media, where no proof was needed at all.

Early on Sunday, Aug. 23, before a morning round at the Trump National Golf Course, Trump paused to communicate to the nation, writing another social media post in what had become a barrage of baseless and false attacks on the integrity of the election system. “So now the Democrats are using Mail Drop Boxes, which are a voter security disaster,” read the president’s posts on Facebook and Twitter. “A big fraud!”

Twitter deployed its system to block disinformation about voting, prefacing the post with a warning: “This Tweet violated the Twitter rules about civic and election integrity.” Facebook let the post stand, though it did affix a link to the message directing users to visit its new Voting Information Center.

The center featured several articles promoting basic voting facts. One was about mail voting. “Voting By Mail (Absentee) Can Be Safe and Easy,” read the headline in August. The post enumerated the standard verification features that mail ballots tend to have but did not directly address false statements about their vulnerability to fraud. (And “can be safe” was hardly a ringing endorsement.)

“Mark seems to be unwilling to put Facebook’s thumb on the scale about what constitutes voter suppression,” Vanita Gupta, president of the Leadership Conference on Civil & Human Rights, told me early this summer, referring to Mark Zuckerberg, the chief executive of Facebook. Gupta was the head of the Justice Department’s civil rights division during Obama’s second term. Now, as the leader of a group representing more than 200 of the nation’s civil rights organizations — including the N.A.A.C.P., the A.C.L.U. and Voto Latino — she was among the few outside leaders with whom Zuckerberg was regularly consulting.

As she saw it, her concerns were up against strong countervailing forces at the top of the company. Zuckerberg had his own absolutist view of free speech in mass media, which always had some regulatory limits in the pre-internet era. His aversion to acting as an “arbiter of truth” had by now been well established. He had also hired from both sides of the political aisle in Washington, in part to convince conservatives that any efforts to crack down on political misinformation would not be aimed specifically at Republicans.

Civil rights groups in Gupta’s coalition had kept a wary eye on one Republican hire in particular: Joel Kaplan, the Facebook vice president for global policy. Kaplan was a veteran of the George W. Bush administration and served as a Bush recount observer in Miami-Dade in 2000. He has acknowledged that he was present at the Brooks Brothers Riot — which he has described as peaceful — but has demurred over the years about his own role in the actual protest. (“While I was there,” he said in a 2003 Senate confirmation hearing, “I was not, to my recollection, a participant.”)

Some civil rights groups had been calling for Kaplan’s ouster since he appeared at the side of his friend (and former Bush colleague) Justice Brett Kavanaugh during Kavanaugh’s contentious Senate confirmation hearings in 2018. Now partisan equivocation seemed to be at play in Facebook’s hesitancy to block Trump’s false statements about mail voting — which had the effect of implying an equivalence between his lies about mail voting and true statements about its well-established viability. “This is rooted more philosophically for Mark, in this notion that Facebook should protect free speech, and a failure to understand what voter suppression looks like today,” Gupta told me in one of several interviews over the spring and summer. This wasn’t an academic issue, Gupta said: In 2018, after she and other civil rights leaders had consulted on an independent audit of its content policies, Facebook created a rule that any post that obviously threatened to suppress votes would be removed.

The action hinged on whether the content fell under Facebook’s definition of “suppression,” which was fairly narrow. For instance, Trump’s post alleging that ballot drop boxes were vulnerable to extensive fraud was similar to the argument his attorneys were making in the lawsuit in Pennsylvania, which wasn’t resolved. In their meetings with Gupta, Zuckerberg and his leadership team would point to such litigation to argue that a claim was in dispute and therefore could not be removed.

What they were failing to understand, Gupta told me, was that the allegation was not only false (and its placement in legal filings didn’t make it less so); it was also more than subtly suppressive. “It confuses voters about what is legitimate and what isn’t,” she told me. “More people will say, ‘Forget it, we’re going to vote in person.’ That could result in not voting at all if Covid comes back.” Polls showed that Trump’s voters were far less concerned about the pandemic and would be therefore less hesitant to vote in person. That was also in part attributable to Facebook; despite its efforts to block misinformation about the coronavirus, content depicting it as a hoax was still abundantly present. (The disinformation video “Plandemic” drew nearly 2.5 million shares, likes and comments on Facebook before the platform removed it last spring, a Times analysis found.)

Facebook was also, Gupta said, playing directly into Trump’s strategy of “sowing the seeds to delegitimize an election he could lose.” During a meeting with Wisconsin Republicans in November, a senior Trump adviser gave a hint about how important social media could be to the campaign’s legal strategy to contest election results if the need arose.

The adviser, Justin Clark, had been describing the effects of a judge’s decision to lift a longstanding ban that kept the Republican National Committee from monitoring polls on Election Day for any irregularities. In 1982, a judge issued the ban after finding that the party illegally used its monitors to intimidate Black voters during Tom Kean’s Republican campaign for New Jersey governor. (Roger Stone was an adviser on that campaign.)

Now, Clark said, the party could use its war chest and vast national network to detect “cheating” by Democrats — in other words, fraud — which could feed lawsuits. “How many times do you have an issue in a county that is just egregious and terrible but it never gets the attention it deserves, because the media won’t report it?” Clark said. “We’ve got a guy who is committed to this, who is able to short-circuit media attention on stuff and just say things.” Social media was the shortest circuit. “Having a presidential candidate — and president — on the Republican side who is talking about the mechanics of voting and potential fraud is something we’ve never had in my lifetime,” Clark told me in late September. “It’s something that’s helpful in highlighting a lot of this stuff and bringing it into the light.”

In late August, Gupta said, events seemed to weigh differently on Zuckerberg. Facebook began to plan contingencies to reduce or remove content in which one side or another claimed victory before any results were finalized. Facebook’s Voting Information Center updated its article on absentee mail balloting, adding a stronger statement that “Voter Fraud Is Extremely Rare Across Voting Methods.” And Zuckerberg and his wife, Priscilla Chan, in an effort to make up for the money Congress wasn’t sending, donated $300 million to fund election-infrastructure development across the country. But as the election approached in late September, Gupta remained uneasy. If Facebook couldn’t enforce its policies, she said, it “would mean disaster for democracy.”

On Wednesday, Sept. 2, Attorney General William P. Barr went on CNN and issued a series of patently false statements about voting. Given his standing as the nation’s most senior law enforcement official, his words also carried an implicit threat. He said there had been several studies that found that mail voting was “fraught with the risk of fraud and coercion,” but he named only one of them, a 2005 report on voting by Jimmy Carter and James Baker III, which actually recommended “further research on the pros and cons of vote by mail.” (A later panel on voting, presided over by Bob Bauer, a Democrat, and Benjamin Ginsberg, a Republican, in 2014 endorsed vote by mail, stating that “fraud is rare.”)

Barr told his interviewer, Wolf Blitzer, that the Justice Department had prosecuted a man in Texas for collecting and filling out 1,700 ballots for the candidate of his choice. The case in question was actually brought locally in Dallas County, and the local prosecutor described it as “tiny” — amounting to charges over a single fraudulent ballot. Barr said that foreign intelligence services could manipulate mail voting and that the national voting rolls were too inaccurate to support an extensive fraud-free mail vote. (Jeffrey A. Rosen, the deputy attorney general, told a panel the week before Barr’s CNN appearance that “we continue to think that it would be extraordinarily difficult for foreign adversaries to change vote tallies.”)

Democrats and civil rights lawyers were watching Barr carefully. No official in Trump’s entire cabinet had as much potential power to affect the election as Barr did. He oversaw the F.B.I., which could start voter-fraud investigations; the United States attorneys, who could bring voter-fraud cases; and the civil rights division, whose lawyers oversaw the enforcement — or lack of enforcement — of the Voting Rights Act.

Barr had his own conservative pedigree on civil rights. As a young lawyer in Ronald Reagan’s Office of Policy Development, Barr co-wrote a memo articulating the rationale animating the movement to roll back civil rights over the decades to come: “We want a colorblind society,” it read. “We do not, for that very reason, embrace the kind of social engineering that calls for quotas, preferential hiring and the other approaches that do nothing but aim discrimination at other racial groups.” Around the same time, Justice John Roberts, then an assistant to the attorney general, was using a similar argument to fight a congressional move to strengthen protections for historically disenfranchised voters in the Voting Rights Act, arguing that it would “establish essentially a quota system for electoral politics.” (Roberts ultimately lost the argument.)

Almost as soon as the Senate confirmed Barr as attorney general in February 2019, he exhibited a willingness to push the department into the service of Trump’s political interest. He had misleadingly played down the findings in Robert Mueller’s report on Russian interference in the 2016 presidential election. He challenged federal prosecutors on the campaign-finance case against the president’s former fixer, Michael Cohen, even though Cohen had pleaded guilty. And after a jury found Roger Stone guilty of lying to Congress, witness tampering and obstruction, Barr withdrew his own department’s tough sentencing recommendation and submitted a lighter one. Stone had said in interviews that the conviction was undermining the work he planned to do to get Trump re-elected. (Trump commuted his sentence in July.)

In the months before Barr’s CNN interview, the department had been making quieter moves on voting. In the spring, it poked into two court fights over mail-in ballots — in Alabama and South Carolina — in filings called “statements of interest.” Statements of interest tend to have no direct bearing on cases, and the filings escaped news coverage. But they are important markers that let judges know where the federal government stands on laws it is authorized to enforce (in these cases, the Voting Rights Act).

The department was not challenging the plaintiffs’ primary arguments that the pandemic had created emergency conditions that required temporary changes. Rather, it was disputing a secondary argument that the three groups bringing the cases, the A.C.L.U., the Southern Poverty Law Center and the Alabama State Conference of the N.A.A.C.P., introduced in their original filings: that the usual requirements that absentee-ballot applications include witness signatures and photocopies of official ID were disproportionately onerous for Black and Hispanic voters during the pandemic — akin to the Jim Crow-era “tests and devices” that the Voting Rights Act made illegal. The message was clear. The Justice Department didn’t want the fight to take place on Voting Rights Act grounds. It was making it all about fraud.

Barr’s mendacity during the Blitzer interview made a lot of news. But there was something else Barr said that much of the coverage missed. Blitzer asked Barr if the president could legally make good on his recent threat to send “sheriffs, law enforcement and U.S. attorneys” to polling stations on Election Day. Barr answered, “If there was a specific investigative danger that we detected some problem and risk — yes.”

He had, of course, just enumerated several “investigative dangers.”

The Biden campaign’s legal team spent the summer gaming out every possible scenario for how Trump could challenge a losing election result. Some of his top advisers were veterans of the voting wars. His longtime aide, Ron Klain, was Gore’s lead strategist during the Florida recount. Bob Bauer, a senior adviser on the team, served on the 2014 voting panel and was Obama’s top lawyer in 2008, when the F.B.I.’s ACORN investigations hit.

At the time, Bauer denounced Republican attempts “to draw the law enforcement process into their attack politics” and called for a special-counsel investigation. In 2020, he was facing a worst-case — and, he still thought, unlikely — scenario involving a Republican president drawing a quasi-military force and extralegal process into his attack politics.

Over the summer, Trump ordered tactical agents at the Department of Homeland Security to combat protesters and rioters in Seattle, Portland, Chicago and Washington. The agents were attached to D.H.S. subsidiaries, including Bortac, the Border Patrol’s SWAT-unit equivalent. They wore neither badges nor insignia as they attacked protesting citizens with chemical agents and even pulled some into unmarked vans.

Biden had been warning for months that Trump would seek to “steal this election,” as he put it in June. Among the campaign’s prospective scenarios was one in which Trump declared that the threat of fraud was so grave that he had to send military-style troops to polling stations. The legal odds were against it. The Posse Comitatus Act generally prohibits using the military for domestic law enforcement. The Voting Rights Act has strict prohibitions against voter intimidation. And the U.S. criminal code allows troops at polls only to counter “armed enemies of the United States.” The question, as Bauer saw it, was whether Trump might try to use a flimsy legal justification for a Department of Homeland Security voting-day deployment. “We’re planning for every nutty thing they can try to do,” Bauer told me.

Roger Stone, newly free of his own legal concerns, provided one such possible justification in an interview in September with the conspiracy-monger Alex Jones: “If someone will study the president’s authority in the Insurrection Act and his ability to impose martial law if there’s widespread cheating,” Stone said, “he will have the authority to arrest Mark Zuckerberg, to arrest Tim Cook, to arrest the Clintons, to arrest anybody else who can be proven to be involved in illegal activity.” The government had once used the Insurrection Act to deploy federal troops to protect Black students arriving at newly desegregated schools and to protect newly freed formerly enslaved Black citizens from Ku Klux Klan attacks during Reconstruction. Now, Stone said, Trump could invoke it to protect all voters from fraud. “The ballots in Nevada on election night should be seized by federal marshals and taken from the state — they are completely corrupted,” he said, arguing that the entire Nevada vote would be fraudulent because the state had approved a plan to send ballots to all voting-age citizens and “they are already flooded with illegals.” In any other year, under any other president, Stone’s rhetoric on an internet-based conspiracy show could be dismissed out of hand. But he had the president’s ear, and the attorney general had intervened in his favor only months earlier.

Barr will be the one to provide Trump with any legal justification, and his rhetoric indicated that he was amenable. “He’s got a choice to make here,” Bauer told me in late September. “Is he actually, beyond his rhetoric, going to support completely unsustainable legal actions, which are going to fail but are going to have a lot to say about how his legacy is viewed by history?” Bauer just wasn’t sure how much of the authoritarian rhetoric was only for show, perhaps in a bid to scare Democrats and depress their vote. In a sense, he said, taking it too seriously could play into Trump’s hands, giving air to Trump’s “wholesale rhetorical assault on the Democratic process.” Nonetheless, Bauer said, the campaign had pre-emptive options to head any extralegal moves off in court, which he declined to share in detail. Bauer believed that in parroting some of Trump’s more outlandish rhetoric, Barr had already undercut the government’s standing before the federal bench.

Barr does have the right to dispatch line attorneys to help monitor polling stations. The Department of Justice has done that regularly since the passage of the Voting Rights Act to make sure jurisdictions complied with it. Trump had his own campaign lawyers ready to bring those challenges, too. Had the Kobach commission finished its work, any lawyers working on Trump’s behalf would have had a huge database from which to make claims — claims that, if recent history had been a guide, would have collapsed in court over time. But in contested elections, charges only need to hold up for long enough. As it happened, Adams’s group had created a private version of that database at PILF, covering 42 states.

In mid-September, PILF released a report called “Critical Condition,” alleging that some 350,000 dead people were on national voting rolls and that tens of thousands were registered more than once, posing a threat to the mail-in voting system. Although at any given moment voter rolls will of necessity contain the names of dead people — no one calls the election board when someone dies — PILF suggested that the report could serve as a basis for “criminal and civil law enforcement investigations.”

Biden had his own allies. Affiliated outside groups like Priorities USA are readying their own legal teams for a litigious November and December. The Democrats will be rowing alongside major civil rights groups that were also watching the election closely, including the A.C.L.U., the Southern Coalition for Social Justice, Fair Fight Action, the Brennan Center and Common Cause. Donors had flooded those groups with money.

But conservatives had a plan for that, too. In Wisconsin, several civil rights groups reported that a man who interviewed their members for a supposed documentary had ties to Project Veritas. In North Carolina, civil rights groups — including the local branch of Common Cause — said an impostor following the Veritas playbook sought to infiltrate their offices. And in New Hampshire, Project Veritas struck its version of gold — one of its operatives found a Democrat who admitted to voting twice in 2016 by posing as a woman. “Voter fraud is real,” O’Keefe tweeted, and on Sept. 24, he posted a video on social media, promising that his biggest exposé on voter fraud was imminent and would serve as an answer to all the doubters.

That same day, the Justice Department had its own answer: Investigators with the F.B.I. and a U.S. attorney’s office were looking into “potential issues” with nine military mail-in ballots that were discarded at the local election office in Luzerne County, Pa. In a breach of protocol, a Justice Department news release revealed that seven of the votes were cast for Trump. Barr had personally briefed Trump, who referred to the investigation on a talk-radio program before the department announced it, portraying it as a fraudulent plot to rob him of votes. The local election board reported a simpler story: A new worker had incorrectly trashed the ballots, and its fail-safes had quickly identified the problem.

The strategy was now in full view: Flood every state, every television news network, every newspaper and news feed with manufactured evidence of fraud to suppress Democratic votes before Election Day — and to knock them out of state-by-state tallies in the courts and counting rooms afterward. In September, Trump’s power to affect the outcome reached a new level when Justice Ruth Bader Ginsburg died and Mitch McConnell lined up the votes for a fast confirmation of the Supreme Court’s sixth conservative member. Increasingly, longtime election experts were seeing “a pathway for something other than voters choosing the next president,” said Richard Hasen, a professor at the University of California-Irvine School of Law who writes the widely read Election Law Blog.

The movement to convince the country that voter fraud is a present danger to democracy has itself become a present danger to democracy. It has melded fully into the president’s re-election campaign. The argument is now that the only way Trump can lose this election is through sweeping voter fraud that benefits his opponent; any outcome in which he doesn’t win, therefore, can be considered illegitimate. This, Trump says, is why he refuses to commit to a peaceful transfer of power: Only fraud can beat him, and fraud is everywhere.

But unlike four years ago, when his campaign laid the groundwork for a similar argument, Trump is now aiming the full force of the United States government — its lawyers, its Postal Service, even its armed officers — at a false threat that has been used to disenfranchise American citizens since the darkest days of the republic. He is doing it in the service of one goal: to maintain his own grip on power.

“When you see them cheating with those ballots, all of those unsolicited ballots, those millions of ballots, you see them, any time you do, report them to the authorities,” he said at a late September election rally in Toledo, Ohio. “The authorities are waiting, and watching.”