HARRISBURG, Pa. (AP) — Pennsylvania catapulted its native son, Joe Biden, to victory and the White House on Saturday after a long, hard-fought and expensive campaign in which Democrats wrested the battleground state's 20 electoral votes back from President Donald Trump after the Republican’s surprise victory in 2016.

Biden also carried Arizona, Wisconsin and Michigan on his path to the presidency, flipping states that Trump won in 2016, but it was Pennsylvania that put him over the top. The state had been a must-win for the incumbent.

The 77-year-old Biden was born in Scranton and sought to contrast his working-class roots with the affluent Trump’s by casting the race as “Scranton versus Park Avenue.” It was a familiar theme for Biden, who has long played up his connection to lunch-bucket Scranton and still has friends there.

“Against extraordinary odds, he achieved what he really wanted, his goal," said lifelong friend Tom Bell, a retired insurance agent who grew up in the same neighborhood as Biden.

Bell called it a win for Scranton, too.

“Scranton is just kind of an old-fashioned city with old-fashioned values," he said, "and people are extremely proud of Joe Biden.”

Biden’s victory came after more than three days of uncertainty as election officials sorted through a surge of mail-in votes that delayed the processing of some ballots, and the Trump campaign mounted several legal challenges that remain pending in the state.

The campaign and the Republican Party argued that GOP election observers were kept too far away from the tabulation in Philadelphia, that some Democratic-leaning counties unfairly allowed people to fix technical problems with their mail-in ballots, and that mail-in ballots arriving after Tuesday should not be counted.

Trump lawyer Rudy Giuliani vowed again Saturday that the litigation would continue next week over the vote count in Pennsylvania. In a statement, Trump vowed not to concede “until the American People have the honest vote count they deserve and that Democracy demands."

Dejected Trump supporters viewed the Pennsylvania results with suspicion, echoing the president's unfounded allegations of a rigged vote.

“I personally do not feel it was an honest win at this point. I really don’t. And if they think this is going to keep the country together, it’s not. It’s just dividing it more," said Debbie Smith, who had a Trump 2020 flag and two signs in her front yard in the Philadelphia suburb of Morrisville.

“I’m not happy,” said Laurie Starner, a retail worker from Mechanicsburg, said at a farmer’s market outside Harrisburg. “I don’t feel like the election was fair.”

A couple thousand Trump supporters rallied peacefully at the state Capitol in Harrisburg, with American flags, Trump flags and “Stop the Steal” signs. Later, about two dozen heavily armed people wearing camouflage joined them.

In Philadelphia, Trump supporters gathered outside the Pennsylvania Convention Center, where votes were still being counted. Outnumbering them was a jubilant crowd of Biden supporters who taunted the Trump supporters and danced to music. Police watched both sides.

The Associated Press declared Biden the winner of Pennsylvania at 11:25 a.m. Eastern time, after determining the remaining ballots left to be counted would not allow Trump to catch up. Biden was ahead by tens of thousands of votes Saturday, a lead that continued to grow as additional mail-in votes were counted.

Biden has long played up the idea that he was Pennsylvania’s “third senator” during his decades representing neighboring Delaware. He also campaigned extensively in the state from his home in Delaware.

Until 1952, Biden lived with his parents and grandparents in a two-story Colonial on a tree-lined street in Green Ridge, an Irish Catholic enclave and one of Scranton’s nicest neighborhoods. Biden slept in an attic bedroom with sloped ceilings and a view of West Mountain, scrawling “Joe Biden was here” and “Kilroy was here” on the walls.

The family moved to Delaware in search of greater opportunity, but Biden returned frequently over the years. He made several stops in northeastern Pennsylvania during the campaign, paying nostalgic visits to his childhood home and the church down the street.

That hometown appeal helped him at the ballot box.

Biden substantially outpaced 2016 nominee Hillary Clinton in Lackawanna County — where Scranton is — after Trump nearly flipped the longtime Democratic stronghold in 2016.

“That was a foundation built over many years, not just his own personal story. He spent 10 years there as a child, and kept coming back in the summers, he came back as a young adult, he had deep roots and deep affection for it. It wasn’t some last-minute thing,” said U.S. Sen. Bob Casey, D-Pennsylvania, perhaps Biden’s biggest cheerleader in Pennsylvania.

In neighboring Luzerne County, where Democrats have steadily lost ground to Republicans, Biden was beaten soundly but still managed to whittle down Trump’s 2016 margin of victory.

Meanwhile, Biden rolled up decisive margins in Philadelphia’s populous suburbs, doing better against Trump than even Clinton, who had racked up historic vote totals there four years ago. Once solidly Republican, the counties have trended Democratic in recent years, with a population that is more racially diverse, better-educated and wealthier than the rest of Pennsylvania.

In Allegheny County, home to Pittsburgh, Biden also appeared to score a larger margin than Clinton as Biden repeatedly courted influential blue-collar labor unions there, saying he would be the strongest pro-union president ever.

On the other side of the ledger, Trump overwhelmed Biden in many of the same rural counties, small towns and exurbs that he won in 2016. In fact, he did even better, underscoring Pennsylvania’s gaping geographic, cultural, economic and political divides. He also managed to squeeze out more votes than last time in Philadelphia — where Trump notoriously said “bad things happen” — though the heavily Democratic city still went big for Biden.

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Rubinkam reported from northeastern Pennsylvania. Associated Press reporters Mike Catalini in Morrisville, Mark Scolforo in Harrisburg and Lemoyne, and Maryclaire Dale and Joe Frederick in Philadelphia contributed to this report.

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Find AP’s full election coverage at APNews.com/Election2020.