In some unions, especially the building trades, support for the
president remains solid despite the efforts of labor leaders to
convince members otherwise.
by Holly Otterbein and Megan Cassella, POLITICO, Sept. 22
https://www.politico.com/news/2020/09/22/donald-trump-union-support-snub-joe-biden-418329?fbclid

"Joe Biden has pitched himself to voters as a “union man,” a son of
Scranton, Pa., who respects the dignity of work and will defend
organized labor if he wins the White House.

"To rank-and-file members in some unions, especially the building
trades, it doesn’t matter. They’re still firmly in Donald Trump’s
camp.

"Labor leaders have worked for months to sell their members on Biden,
hoping to avoid a repeat of 2016 when Donald Trump outperformed among
union members and won the White House. But despite a bevy of national
union endorsements for Biden and years of what leaders call attacks on
organized labor from the Trump administration, local officials in
critical battleground states said support for Trump remains solid."
. . .