PITTSBURGH — The case for Joseph R. Biden Jr. has always come down to Pennsylvania.
It is not just that the former vice president, who jumped into the presidential race last week, is a native son of a state that is a 2020 must-win for Democrats.
The argument is that Mr. Biden’s brand of politics — appealing to a traditional coalition shredded by Donald J. Trump in 2016 — still has latent appeal in Pennsylvania and across the Midwest, and that stitching the coalition back together would restore Democrats to the White House.
Mr. Biden’s entry was met, particularly on social media, by a chorus of doubts at times bordering on derision from critics and progressive activists who questioned his age, his status as a white man and his political luggage from more than four decades in public life.
But as Mr. Biden prepares for his first appearance of the campaign, at a union event in Pittsburgh on Monday, interviews across the state last week indicated that he draws from a wellspring of support among three key constituencies crucial to his campaign. He has the potential to attract suburban moderates defecting from the Republican Party under President Trump, to invigorate black voters who were underwhelmed by Hillary Clinton and to reverse at least some losses among working-class white voters.
At Uncle Bobbie’s Coffee & Books in the Germantown neighborhood of North Philadelphia, black empowerment was on prominent display via titles like “White Fragility” and “What Doesn’t Kill You Makes You Blacker.”
But when the talk turned to presidential politics, patrons universally said Mr. Biden was at or near the top of their list, in no small part because of his eight-year partnership with President Barack Obama.
“Just to be in the house and assisting Barack when he was in the house, he would already have my vote for that alone,” said Ciarra Walker, 30, a small-business owner.
Kerry Chester, 53, a network engineer working at his laptop, said he voted for Senator Bernie Sanders of Vermont in the 2016 Pennsylvania primary. But for 2020 he thinks it is so important to defeat Mr. Trump that Mr. Biden is preferable, even compared to the two top African-American candidates, Senators Cory Booker of New Jersey and Kamala Harris of California.
“I’m going to be completely honest: I think with the country going the way it is, I think we’re kind of safer on the Democratic side going with a white male right now,” he said.
Neither Mr. Chester nor other black voters interviewed said Mr. Biden’s record of championing anti-crime bills — as a Delaware senator in the 1980s and ’90s — that led to mass incarceration were impediments to their support.
“That was 20 years ago,” Mr. Chester said. “I can’t hold everything against him.” He added that compared with other candidates, “I trust him a lot more.”
Nasya Jenkins, 21, who works at a Boys and Girls Club and is an aspiring influencer on Instagram, said she did not penalize Mr. Biden for his treatment of Anita Hill in her 1991 Senate Judiciary Committee testimony. Mr. Biden called Ms. Hill recently to address some of her concerns, a conversation she said left her dissatisfied.
“I’m not really so caught up on what happened in the past,” Ms. Jenkins said. “We’re here now, with all the problems we have. What do you plan on doing to change that — period?”
Jeffrey Cooper, 51, who was waiting for a bus at the Olney Transportation Center in North Philadelphia, suggested that the best nominee to close that gap would be Mr. Biden.
“Joe Biden has a connection with the African-American people,” said Mr. Cooper, a computer programmer. “If Joe Biden comes here personally — walks among the people — if he does that a few times, he’ll get the votes of the people.”
Representative Dwight Evans, whose district in Philadelphia is majority African-American, said,“I think of all the candidates — nothing against any of those other candidates — he is in the best position, and has the best skill set necessary to become the next president.”
Mr. Biden is targeting a swath of voters — including older, less educated and less liberal Democrats — who are often ignored by other candidates chasing younger voters more in keeping with the leftward energy in the party.
And to many Democrats, the worst-case scenario in a field of historic diversity would be the nomination of a septuagenarian white male moderate. If activists coalesce behind alternatives to Mr. Biden once primary voting gets underway next spring, the landscape could look much different than today.
Still, a Muhlenberg College poll of Pennsylvania this month showed that 45 percent of Democrats identified as moderate or conservative, and they strongly favored Mr. Biden over his closest rival, Mr. Sanders. Voters older than 50, a majority of registered Democrats, prefer Mr. Biden to Mr. Sanders by blowout margins. Over all, Mr. Biden led Mr. Sanders in the statewide poll of registered Democrats, 28 percent to 16 percent.
An hour north of Philadelphia, another key chapter in the story of Mr. Trump’s 2016 victory was written in Northampton County. A surge by white voters without college degrees helped Mr. Trump flip a county Mr. Obama easily won in 2012.
Robert Micklus, 73, retired from the iconic Lehigh Valley employers Bethlehem Steel and Mack Trucks, and his wife, Judy Micklus, 71, a retired forklift driver, are both registered Democrats who voted for Mr. Trump. They liked his tough talk on immigration. Both are unsure if they will choose him again in 2020. “Sometimes he acts like an idiot,” Ms. Micklus said, adding with a sigh, “He’s trying.”
Like many other vestigial Democrats who strategists sometimes call “Trump triers,” they yearn for a less polarized country.
“Joe Biden,” Mr. Micklus said, turning over the familiar name and resonance of a man born a couple of counties over in Scranton. “It’s possible,” he said of the chances a Biden nomination could lure him back to the Democratic fold. “My impression is he seems like an honest guy.”
Kevin Frantz, a 60-year-old retired firefighter, is already a committed Democrat. He said Mr. Biden would be the most likely nominee to defeat Mr. Trump.
“I like his sincerity, his personality, his experience,” he said. He added, “I think he cares.”
Mike Mikus, a political consultant in Pittsburgh who also advises unions, recalled that Mr. Biden was greeted warmly at last year’s Labor Day parade in the city. “It’s one of the largest Labor Day parades in the country,” he said. “They were all yelling, Please run, Joe!”
Mr. Sanders, too, is competing for white voters without a college degree. He recently defended his policies on “Medicare for all” and free public college, and his opposition to trade deals — which have pushed the party leftward — during a blitz of Midwest states.
“The reason we are visiting these states is pretty simple: Donald Trump won them two and a half years ago, and we’re not going to let him win them in 2020,” he told a crowd of thousands in Pittsburgh.
The Muhlenberg College poll showed that Mr. Biden’s greatest weakness was with younger voters. He was the choice of only 5 percent of Democrats under 30, compared with 40 percent for Mr. Sanders.
One of those voters is Ian Gallagher, a 24-year-old casino employee from Northampton. The argument that Mr. Biden’s center-left politics makes him more electable “doesn’t do it for me,” he said. “We need way more left than center-left. Center-left was Obama, and that didn’t work out.” He favors an Elizabeth Warren-Bernie Sanders ticket, with Ms. Warren at the top.
The third potential leg of a Biden coalition is in the suburbs, specifically communities where college-educated voters who traditionally prefer Republicans have defected under Mr. Trump.
In a special election for a State Senate seat in the suburbs south of Pittsburgh on April 2, a Democrat flipped a district that Mr. Trump had won by six points.
“This is such a Republican area but everybody secretly voted Democratic,” said Barbara Zimmt, 62, a fund-raiser and volunteer for the library in the suburb of Upper St. Clair.
Electability is the argument that consumes suburban Democrats.
It has led voters like Ms. Zimmt — even though she would love to see a woman as president — to land on Mr. Biden. “I guess it would be Biden at this point, because I think he can win,” she said.
“I think a lot of people are scared of the progressives,” said Sarah Tannenbaum, 35, a part-time accountant in Upper St. Clair. “Someone more moderate will have a better chance of defeating Trump.”
Beth Friedman, 38, a stay-at-home mother visiting the Upper St. Clair library with her children, voted for Mr. Trump in 2016, in part because her father is a former coal miner. Mr. Trump promised to bring back coal. But she said he does not deserve re-election because of “this whole wall thing” on the southwestern border.
Although she has not yet tuned into the 2020 race, Ms. Friedman seeks a centrist candidate. Could that be Mr. Biden? “I probably would vote for him,” she said.
There were dissenters from the argument that Mr. Biden is most electable. “I think he’s too old, has too much baggage and can’t win,” said Pat Flanigan, a community banker who lives in Upper St. Clair. He described the suburb as undergoing political transition. “A lot of the older rich Republicans are handing off to rich Democrats now.”
He favors Ms. Harris, who he said brings “a fresh voice and a new perspective.”
The name of Ms. Harris, a former attorney general of California, was mentioned as a top choice by many of the same people leaning toward Mr. Biden, including patrons of Uncle Bobbie’s in Philadelphia and suburbanites in Upper St. Clair. It was a reminder that the race is in its early stage, and coalitions could break apart and reconstitute multiple times around someone new.