WASHINGTON (Reuters) - 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. 

If elected, Harris would make U.S. history as the first female and second Black president, and sexism and racism have been seen as a hurdle to her winning.

Liz Shuler, president of the 12.5 million-member AFL-CIO, said enthusiasm for Harris is strong overall but sexism is likely undermining support for her in some unions.

"Let's be honest, there are people who look at a female candidate and at face value dismiss her because, you know, she's perceived as not being presidential," she said. "No one questions Donald Trump in that way."

Finding these men at home can be a challenge and the AFL-CIO is addressing the problem instead by visiting men at their job sites, where chances of a conversation to address their concerns are much higher, she said.

The problem is especially acute within the building trades unions like electricians and pipefitters, whose members are predominantly male and white. 

Larger service unions, where membership is more diverse, have witnessed a growing gender gap, where a drop in male support has been offset by a surge in support from women, labor officials say. 

It's part of a phenomenon playing out across the country that could be a pivotal factor in the election, Reuters polling shows - Harris is gaining with women, especially white women, while Trump is polling better with men than he was in 2020. 

James Maravelias, head of the Delaware AFL-CIO, said Harris' support among male members has been weaker in part because of her liberal track record on social issues and in part because of male chauvinism.

"I am afraid some won't come out at all," Maravelias said about potential impact on Election Day.

In interviews, AFL-CIO door knockers said some households view Harris and Democrats as strong defenders of union rights while others have lost faith in the Democratic Party and see more common ground with Trump.

"The men are the toughest doors," said one of six door knockers interviewed. "They want to argue and there's no agreement on the facts."

An AFL-CIO-led door-knocking effort in the Philadelphia area was forced to narrow its focus to known Harris supporters after an expected wave of volunteers failed to materialize, according to a local organizer.

Most major unions have endorsed Harris, including the United Auto Workers union, but it is a mixed picture at the rank-and-file level across industries and different parts of the country.

POLL FAVORS HARRIS, BUT WILL IT BE ENOUGH TO HELP HER WIN?

Support for Harris remains strong in Racine, Wisconsin, said Richard Glowacki, chairman of the UAW Local 180, which represents workers at a CNH Industrial's sprawling tractor factory on the outskirts of that faded blue-collar city. 

He called demand for Harris' and other Democrats' yard signs "unreal" and said retirees are actively getting out the vote.

But the 1.3 million-member International Brotherhood of Teamsters, representing workers ranging from airline pilots to zookeepers, decided not to endorse a candidate in this election after a poll of members found Trump led Harris by 59.6% to 34%. 

A Reuters/Ipsos poll showed Harris leading Trump 47%-36% among Americans who were union members or had a family member in a union. The survey of 655 union household respondents was held Oct 16-21 and had a margin of error of about 4 percentage points.

In the 2020 election, Biden had a 16-point advantage over Trump - 56% to 40% - in an Edison Research poll of people who lived in households with a union member.    

Lauren Hitt, a spokeswoman for the Harris campaign, said steep losses in support among non-college educated males could be made up by gains from non-college educated women. The Trump campaign did not immediately respond to a request for comment.

UNION VOTES MATTER 

Union workers make up one-fifth of the voters in battleground states Michigan, Pennsylvania and Wisconsin, says the AFL-CIO, the largest federation of unions in the country that counts several building trades unions among its members.

The three states, known as the "Blue Wall" for their importance to Democrats, are among the seven battlegrounds that will decide Tuesday's presidential election. 

Unions are also key to Democrats' "Get out the vote" efforts in these states, and their members traditionally knock on thousands of doors ahead of elections to rally voters. 

Harris, who is also of South Asian origins, has dismissed concerns that sexism could hurt her chances of winning the White House, saying the country is "absolutely" ready to elect a female president. 

Jimmy Williams, president of the International Union of Painters and Allied Trades (IUPAT), which has over 140,000 members, said a drop in support from men is being more than offset by women within his union.

"I have spoken to women members in the states of Pennsylvania, Michigan, Wisconsin, and Ohio and I can tell you, not one woman member that I have spoken to, has been somebody who has been supportive of Donald Trump, not one," he said.