In his campaign's TV ads, Pennsylvania Republican House candidate Rob Bresnahan talks about being a third-generation union contractor. His brochures claim he has created well paying union jobs.

These union ties are a key part of Bresnahan's pitch to voters as he campaigns in the hopes of unseating incumbent Democratic Rep. Matt Cartwright.

It's not surprising for a candidate in northeastern Pennsylvania to trumpet their union ties. But it is very surprising for a Republican to be the one doing it.

"Just because I have an 'R' next to my name doesn't mean that I'm not for collective bargaining," Bresnahan said at a local bar recently, before ticking through part of his resume: Chairman of the Joint Apprenticeship Training Committee, which helps train electrical apprentices and workers, and health wellness and annuity trustee, which ensure union members receive health and retirement benefits.

"I was always able to put my hat on and say, what's best for this organization at this time?" said Bresnahan who, while not a union member himself, has a history of working closely with them.

Bresnahan's pitch to union workers comes as Republicans including former President Donald Trump and vice presidential nominee Sen. JD Vance (R-Ohio) are seeking to win the support of individual union members, even while union leaders stick by Democrats.

Support from unions is critical in Pennsylvania, where union members make up 14.1% of the state, according to the Bureau of Labor Statistics. That makes them a must-win group in a must-win state for not just control of the White House, but also the Senate and the House, according to election forecaster Cook Political Report.

NBC News polling data shows that over the past decade, union households have increasingly favored Republicans in both presidential and congressional races. A majority of union households still prefer Democrats, but in close races like Bresnahan's – which is rated a toss-up by Cook Political Report – a few thousand votes can make the difference.

Cartwright has held his seat in the House for more than a decade, even as the area has grown increasingly conservative.

In 2020, Cartwright won reelection in his district with 52% of the vote. But in the presidential race, Trump won it, with 51% of the vote, according to NBC data. Two years ago, Cartwright won just 51% of the vote.

Pennsylvania's 8th congressional district is 72% white, with a median household income of $61,140 in 2023, according to the U.S. Census Bureau.

At the Sheet Metal Workers Local 44 Union Hall in Wilkes-Barre in early October, local union leaders frequently referred to Cartwright as a "friend." They praised Cartwright for backing pro-union policies and helping bring millions in federal funding to the district, thanks in part to his role on the powerful appropriations committee.

"He supported us," said Keshia Williams, a certified nursing assistant and SEIU member. "He's been on the picket lines with us for nursing home workers and hospital workers alike. He's brought in a lot for our communities, our local communities."

Cartwright said his loyalty to unions is deeper than elections.

"In northeastern Pennsylvania, it goes beyond that. It goes to our heritage. It goes to our bloodlines," Cartwright said. "All of the people here had ancestors who not only worked in the mines, but also benefited from the efforts of organized labor."

Cartwright has the backing of numerous unions in the area, including locals chapters of the Teamsters, SEIU and AFL-CIO.

Bresnahan is relying less on major endorsements and more on appealing to individual union members, like the ones he has worked with through his membership with the National Electrical Contractors Association, a group that has a long partnership with the International Brotherhood of Electrical Workers, or IBEW.

While he doesn't entirely back major pro-labor legislation like the PRO Act, Bresnahan said his stances on other issues like immigration resonate with union members.

"Border security is very important to a lot of people, specifically union members, who work every single day," Bresnahan said in an interview with CNBC. "They give it their all. They're the best at what they do, and they feel that they're getting put second to perhaps 10, 12, 15 million illegal migrants that have been coming to the country illegally."

Bresnahan is running for office for the first time this year after a career at his family's business, Kuharchik Construction, which he joined as CFO when he was 19. He then took over as CEO.

Bresnahan has been criticized by opponents for selling his company to a Canadian private equity firm. Bresnahan has pushed back, saying he still is an owner in the company and that the move ultimately created more jobs.

But the nuances haven't made any difference to Travis Buchanan, a local union worker, said he voted for Cartwright in the past and thinks Cartwright is good for unions. But he sees Bresnahan has good for unions and on other issues like immigration and inflation.  

"We're doing things to make sure that we're all take all of our wants and needs into account, not just our labor side of things," he said. "If we can get a candidate that does both, that's amazing. That's what I see in Rob."

There is also growing sense among some union members that Democrats aren't doing as much as they could for them. Teamsters President Sean O'Brien said on a podcast that Democrats "f–ked us over for the last 40 years."

The Teamsters declined to endorse a presidential candidate this year, and O'Brien both spoke at the Republican National Convention.

The firefighters unions also voted against giving either candidate the nod, after being one of the first to endorse Biden in 2020.

Yet, Cartwright said that the Democrat's pro-union policies ultimately make the point that it's his party who is best for workers.

"Most union members understand that it's the Democratic Party that sticks up for the little guy and gal," he said. "And and it's the Republicans that are always trying to to gut union rights."