PHILADELPHIA – About an hour into door-to-door election canvassing Saturday, letter carrier Charlie Holesworth, a volunteer with the AFL-CIO, met a young married couple who confided to being at loggerheads about their presidential choices.

“We try not to talk about it too much because it gets ugly,” Bernadette Cannon told Holesworth, explaining her support for Hillary Clinton while standing in the driveway of her duplex. “I’m hoping she wins in a landslide,” she said.

“I’m undecided,” her husband, Jeremy, added while herding their two rambunctious kids out of the family car and into the house. “I’m definitely not about Hillary. I certainly don’t trust her.”

Bernadette Cannon, a public school teacher, said in a near whisper that she was “working on” her husband, hoping he would decide not to vote for Donald Trump. The Republican nominee’s inflammatory rhetoric and behavior in the final weeks of the campaign had bolstered her pro-Clinton arguments at home, she said, although her husband’s family – populated with Trump supporters – was influential as her spouse weighed his choice.

“One of the things you should put on the questionnaire when you’re dating, right? You check the bank statement. You check the family. It was like, `You’re Republican? Really? How did that happen?’” she joked.

Holesworth laughed and told her the labor federation supported Clinton and Senate candidate Katie McGinty, who is neck-and-neck in Keystone State polls as she tries to unseat GOP incumbent Pat Toomey.

The 43-year-old teacher said she was unsure how she would vote in the Senate race, and her husband told their visitor he “could care less” about that contest.

“This year, Pennsylvania is so important. It’s coming down to Philly and the suburbs,” Holesworth told Bernadette. “Even if we have a lead now, in three weeks, who knows what could happen,” he added.

For more than two hours, Holesworth worked alongside Bridget Fitzgerald (pictured), a union volunteer from southern Maryland who is a member of the International Association of Machinists and Aerospace Workers. They knocked on dozens of nearly identical Halloween-decorated doors, listening carefully to how middle-class Philadelphians said they planned to vote.

When they encountered Trump supporters, primarily middle-aged white men who said they favored conservative values and disliked the former secretary of state, the canvassers were polite. “I had to bite my tongue,” Fitzgerald said several times. Holesworth added, “We don’t try to change their minds.” When no one answered at the addresses they were instructed to visit, they left fliers explaining why organized labor stopped by.

Guided by data sheets and a smartphone app, the pair gathered information from residents on their lists who happened to be home. The preferences were uploaded later to a central database that will help determine which Democratic-leaning union members or households are telephoned or visited again before Nov. 8 as part of a get-out-the-vote drive aimed at keeping Pennsylvania blue. Clinton continues to lead Trump by nearly seven percentage points in the RealClearPolitics Average of Pennsylvania polls, which includes third-party candidates.

With 20 electoral votes on the line, the state is one of half a dozen presidential battlegrounds with competitive Senate races. The combination of Clinton’s contest and the possibility of flipping the Senate into Democratic hands is tantalizing to the political arm of the American Federation of Labor and Congress of Industrial Organizations. Other states on unions’ radar are Florida, Nevada, Ohio, North Carolina, and Wisconsin. Beyond 2016, organized labor already is plotting to help influence 2018 and 2020 races, including contests for governor.

Without a win in Pennsylvania, Trump’s pursuit of 270 electoral votes may fall apart. To defeat Clinton in a state that voted Democratic in the past six elections, the GOP standard-bearer must rack up sufficient votes outside heavily progressive and populous Philadelphia and its leafy suburbs.

Unions are among the groups with sophisticated ground operations dedicated to driving turnout for favored candidates -- in this case based on issues including opposition to international trade pacts, support for collective bargaining, and backing for economic policies that benefit low- and middle-income workers and their families. The AFL represents more than 12 million active and retired workers from 56 national and international unions.

“Since 2012, when we do walks in neighborhoods, we’ve built more capacity and are talking to both union members and non-union people in those neighborhoods,” Michael Podhorzer, political department director for the AFL-CIO, told RealClearPolitics in an interview. “Non-union people don’t have the perspective that union members get at work, but they’re neighbors. Our walk program is all volunteer, so it’s people … in those communities talking to their neighbors, and that has credibility,” he added.

Podhorzer said he could not estimate what the AFL’s political operation would spend this cycle, but the non-partisan Center for Responsive Politics estimates the AFL-CIO has spent $11.4 million thus far.

Holesworth and Fitzgerald were among 360 union volunteers who fanned out to five locations in and around Philadelphia on Saturday morning. Labor representatives also organized a rally downtown and invited local news media to the event. Such door-knocking will take place daily and on weekends until the program shifts to mobilizing like-minded voters on Election Day (Pennsylvania does not permit early voting and requires an excuse to vote absentee).

An internal AFL poll conducted before Labor Day challenged Trump’s boast that rank-and-file union workers strongly backed him for president, despite a long list of endorsements from union leaders for Clinton. The AFL’s survey, which focused on union households in Florida, Nevada, Ohio, Pennsylvania and Wisconsin, showed Trump with about 36 percent of union-member support at summer’s end. Public polls reported similar results.

Saturday’s canvassers in Philadelphia’s Holmesburg neighborhood tried to talk to potential voters about the policy agenda Clinton supports, aware that the Democratic nominee earns low marks from the public when it comes to appraisals of her honesty and trustworthiness.

“I don’t want to vote for either one of them,” said resident Thomas Niemiec, who works for the Southeastern Pennsylvania Transportation Authority. He said he doesn’t like Bill Clinton and “what he’s into,” and thinks Trump has “a big mouth.”

“I can’t wait until this thing is over,” he added ruefully. “I’m probably going with Trump.”

Niemiec was not the only one. Kelly Barber, 38, an IT database administrator, said she is undecided, but is registered as a Republican and considers Clinton “way too liberal” for her tastes.

Michael Dunn, 62, a retired pipefitter, said he voted for Barack Obama in 2008 and subsequently thought he made a mistake. “I’m not listening to my union this time,” he added. “I like the Republican values.”

Union members’ departure from their leadership’s endorsed candidates “is always a concern,” Patrick Eiding, president of the Philadelphia Council of AFL-CIO, said. This year’s resistance to Clinton reminded him of hurdles in 2008 when union members took stock of the first African-American presidential nominee.

“I think we see the same thing here a little bit, and it’s kind of scary because the negativity coming out on both candidates makes the discussion a little different,” said Eiding, who is 76. “Our work really is to try to talk to as many members directly about the issues, and the issues are pretty important. … But I think the [members] we don’t get to are the ones that make us nervous because two things may happen: They may not vote at all, and some of them are just caught up in the lies because they’re frustrated.”

Labor leaders insist that persistent questions about Trump’s governing agenda when it comes to working Americans, on top of what they describe as his greed-is-good track record as a developer with a penchant for stiffing contractors and filing for bankruptcy, may ultimately sway reluctant rank-and-file union members to back the Democratic nominee.

“There’s a lot to debate or look at with Hillary Clinton because she’s been out there on the front line for a lot of years,” Eiding continued. “With him, it’s just believing what he says.”

An estimated 18 percent of the electorate this fall is likely to be made up of union members and those living in a union household, about the same percentage as backed Obama in 2012. The number of union workers in America as a percentage of the workforce, however, has been on a decades-long decline.

Nonetheless, the influence of labor unions and their members in past election cycles has been demonstrable, worth about two to three points nationally in 2012, according to some analyses.

Unionized workers in the United States have historically been more likely to be Democrats, and they are also more likely to turn out to vote, said Peter Francia, professor of political science at East Carolina University and author of the book “The Future of Organized Labor in American Politics.”

“The union variable -- membership in a union or even membership in a union household -- is really a very strong predictor of increasing the likelihood of voting for the Democratic candidate,” Francia told RCP. “So unless Donald Trump breaks the mold here … there are many, many election cycles that bear that out.”

As a shrinking percentage of the workforce, labor unions have tried to maximize their political impact using what they’ve still got. Their numbers, political consensus and ultimate clout are not guaranteed, however.

“Over the years, they’ve tried to overcome it with really aggressive get-out-the-vote efforts,” the professor added, “but if you keep losing membership, that game gets harder and harder to play.”

On Saturday in Philadelphia’s suburbs, the Trump effect was still a 2016 wildcard.