MT. LEBANON, Pa. — When Joseph R. Biden Jr. came to the Pittsburgh suburbs in 2018 to stump for Conor Lamb’s long shot special election campaign, he made a pitch directly to the sort of blue-collar union workers who had abandoned the Democratic Party when Hillary Clinton was on the ballot.
“I don’t know all of you personally, but I know you,” Mr. Biden said at a rally a week before Mr. Lamb became the first Democrat to flip a Republican House seat during Donald Trump’s presidency. “I know this state. I know this region. I know what it’s made up of. I know the values that underpin all of what you believe in — family, community, again, not leaving anybody behind.”
Two and a half years later, Mr. Biden is preparing for a virtual party convention, beginning on Monday, that will formally install him as the Democratic Party’s 2020 presidential nominee. He arrived at this moment with a sizable lead over President Trump in the polls, using a playbook first employed to success by Mr. Lamb two years ago, and then borrowed by dozens of Democrats during the midterm elections later that year.
Mr. Biden has repeatedly returned to the same themes and strategies that supported Mr. Lamb to a surprise, if razor-thin, victory in a district that Mr. Trump carried by about 20 points in 2016 — and where Democrats were so insignificant that they not fielded a candidate since 2012.
Mr. Lamb’s victory showed Democrats how to prevail in Republican territory during the Trump era: focus on kichen-table issues; inspire defections from college-educated suburban voters — especially women — who had been core Republican voters for decades; and offer conservative-leaning voters a sober, reassuring alternative to a chaotic president.
It helped that Mr. Lamb was a Marine veteran and a former federal prosecutor — a résumé of service to the country that he and fellow Democrats used to contrast themselves with Mr. Trump and Republicans who came from the business world.
Mr. Biden has likewise used his decades of experience in the Senate and eight years as vice president to highlight his own public service, while reminding audiences that he regularly ranked among the least-wealthy senators to demonstrate his commitment to the middle class.
Though Mr. Trump twice traveled to Pennsylvania to hold rallies for Mr. Lamb’s opponent, Mr. Lamb, seeking to distance himself from his party’s left-leaning brand, turned away entreaties from nearly all ambitious national Democrats interested in stumping for him — all except for Mr. Biden, with whom he spent a day traversing the district speaking to union workers.
“There are a lot of people who voted for me in 2018, not so much for reasons of policy or party, but just reasons of change,” Mr. Lamb said from atop a picnic table during an outdoor interview this past week in a park near his home in Mt. Lebanon, a suburb. “People were unsatisfied with how things were going, and I promised that I would do my job differently than the guy you had before me. And I think that’s what Vice President Biden is basically doing.”
There is no guarantee that Mr. Biden can replicate Mr. Lamb’s path to victory. Mr. Trump has retained devout loyalty from Republican voters. A November presidential contest will drive turnout far higher than in the special election in which Mr. Lamb won his surprise victory, or the 2018 midterm elections when Democrats won a sweeping triumph in the nation’s suburbs.
When Mr. Lamb won in March 2018, he served notice for Democrats aiming to wrest control of the House and give the party control of at least one lever of the federal government. The answer to defeating Trump-aligned Republican candidates was not to emphasize the president’s erratic, divisive tenure in the Oval Office. Instead Democratic candidates focused narrowly on policies affecting voters’ lives, like protecting provisions in the Affordable Care Act and casting Republicans as a party pandering to corporations and the very rich, attacking the 2017 tax cut that Republican Party leaders had intended to use as the tent pole achievement for their midterm campaigns.
During his remarks at Mr. Lamb’s rally, Mr. Biden called the tax cut “obscene.”
“It’s really hard to screw up a tax cut, but they managed to do it,” said Meredith Kelly, who was then the communications director for the House Democrats’ campaign arm. “It set a narrative that fit very nicely into what Biden has done.”
In Congress, Mr. Lamb is a rank-and-file Democrat who has not rocked the boat or voted against the party’s leadership on any significant issues. At home, he’s cultivated an image of a Democrat focused on Pennsylvania jobs above all else — a sentiment he says Mr. Biden has echoed.
“No matter what side of an issue my party was on when I went to Washington, I would be fighting for their jobs no matter what,” Mr. Lamb said. “How many times did Vice President Biden use the word ‘jobs’ in his speech about energy and climate change? He used the word ‘jobs’ a million times. He was talking about climate change, but kept reminding people that this is a policy that’s about their jobs. And I think, to me, that was him taking that lesson too, that that’s ultimately what people care about the most.”
When Mr. Biden’s presidential campaign began, he ran on a platform that was far less flashy than his top rivals, progressives like Elizabeth Warren and Bernie Sanders. He wasn’t for a single-payer health care system or adding extra Supreme Court justices or funding an array of new federal programs with a wealth tax on millionaires.
Instead Mr. Biden’s platform looked a lot like what Mr. Lamb ran on in 2018: protecting Social Security, Medicare and health care while opposing tax cuts for corporations and the wealthy. And even though he’s adopted an array of more liberal-leaning positions since becoming the presumptive nominee, Mr. Biden is still viewed as a politician most concerned with working-class Americans.
“People say the same thing about Conor and Joe,’’ said Representative Mike Doyle, a Democrat whose district abuts Mr. Lamb’s. “Here in Western P.A., someone will say he’s a regular guy. That was a Trump plus-20 district, and he won it because he stuck to the things the people in Western Pennsylvania really care about and because people thought he was an average guy. He’s a regular guy. He’s one of them, and Joe’s one of them.”
Polls show that in addition to suburban voters, Mr. Biden is having success in breaking Republicans’ longtime lock on older voters. A Fox News poll of Pennsylvania last month found Mr. Biden leading Mr. Trump by seven percentage points among voters 65 or older. Exit polls in 2016 found Mr. Trump won older voters by a 10-point margin.
Ralph Perkins, an 89-year-old retired mining engineer from Canonsburg, Pa., 20 miles southwest of Pittsburgh, said he was likely to vote for Mr. Biden after casting a ballot for every Republican presidential nominee since Dwight D. Eisenhower in 1952.
The one thing that could lead him to vote a second time for Mr. Trump, Mr. Perkins said, would be if Mr. Biden supported defunding the police. But after calling the local Washington County Democratic chairman, Ben Bright, Mr. Perkins said his fears were allayed.
“Biden, I think he’s very much superior to Trump,” Mr. Perkins said. “Do I think he’s perfect? I’m not head over heels for him, but I think he’s fine.”
Mr. Bright, who began volunteering for the party after Mr. Trump’s 2016 victory and became the county chairman in 2018, said Mr. Biden appeals to the same type of voters who crossed party lines to back Mr. Lamb.
“The main issues that Democrats stand for now are what Conor ran on,” Mr. Bright said. “Affordable health care, good-paying jobs for middle class people, strengthening unions and better public education.”
Mr. Lamb’s 2020 Republican opponent, Sean Parnell, an Army veteran, out-raised him by more than $270,000 during the three-month period ending on June 30. Still, Mr. Lamb is favored to win re-election in the district, which was redrawn in his favor by the Pennsylvania Supreme Court after his March 2018 victory.
Republicans discount Mr. Lamb’s victory as an aberration, the result of a flawed opponent who failed to raise a significant amount of money and Mr. Lamb’s squeaky-clean image that, they say, has been tarnished by more than two years of voting for Democratic priorities in the House.
Rick Saccone, the Republican state legislator who lost to Mr. Lamb, “wasn’t the best candidate we could have fielded,” said Rob Gleason, a former chairman of the Pennsylvania Republican Party.
Mr. Saccone, who during the campaign called himself “Trump before Trump was Trump” in an attempt to appeal to the president’s supporters, said the anti-Trump energy in Pennsylvania would make it “tough” for the president to win the state again. He attributed his own loss to Mr. Lamb’s refusal to embrace some of the Democrats’ more liberal positions on the environment and social issues.
“When they had a choice between a conservative Republican and someone who looked like a conservative Democrat, they went with the Democrat,” Mr. Saccone said.
In the interview last week, Mr. Lamb was clear about why he embraced the support from Mr. Biden, and few others.
“Although everyone knows he’s a Democrat, he really understands western Pennsylvania,” Mr. Lamb said. “I couldn’t think of anybody on a national stage that kind of speaks the language of western Pennsylvania better than him. And I think he helped us draw attention to the fact that I was kind of a Democrat of the old school and someone that people can trust to fight for them.”