With the U.S. election days away, Vice President Kamala Harris is struggling to secure the support of male volunteers in some labor unions whose phone calls and house visits are needed to get Democratic supporters out to vote, senior labor officials said.

Most unions have long supported Democratic candidates, and both Harris and President Joe Biden have backed unions in contract negotiations and championed workers' rights.

But Republican candidate Donald Trump, who was president from 2017-2021, has made inroads with union workers in recent years and any drop in support for Harris could be a decisive factor in the neck-and-neck race.