SCRANTON, Pa. (AP) — President Donald Trump cast doubt in advance on Tuesday's election results, while Democratic challenger Joe Biden pushed ahead on offense on the final full day of campaigning ahead of an election conclusion that could have consequences for the U.S. for years to come.

The president threatened legal action to stop vote counting in crucial states including Pennsylvania, where both candidates campaigned Monday, and his advisers put out a statement accusing Democrats of trying to “subvert state deadlines for receiving and counting ballots.”

If Pennsylvania ballot counting takes several days, as is allowed, Trump charged that “cheating can happen like you have never seen. ”

Biden dipped into Ohio, a show of confidence in a state that Trump won by 8 percentage points four years ago. He focused on the central message of his campaign: that Trump cost lives by mismanaging America's response to the worst pandemic in a century.

“Donald Trump is not strong, he’s weak," Biden declared in Cleveland. "This is a president who not only doesn’t understand sacrifice, he doesn’t understand courage.”

On the eve of the election, the U.S. is at a crossroads, gripped by a historic pandemic that is raging anew in nearly every corner of the country, and a reckoning over race. Both campaigns insist they have a pathway to victory, though Biden’s options for picking up the required 270 Electoral College votes are more plentiful. Trump is banking on a surge of enthusiasm from his most loyal supporters in addition to potential legal maneuvers.

Trump was spending the final day sprinting through five rallies, from North Carolina to Wisconsin. Beyond Ohio, Biden was devoting most of his time to Pennsylvania, where a win would leave Trump with an exceedingly narrow path.

The two men delivered their final messages, with Biden emphasizing the pandemic. He declared that "the first step to beating the virus is beating Donald Trump,” and he promised he would retain the nation’s leading infectious disease expert, Dr. Anthony Fauci, whom the president has talked of firing.

Trump, meanwhile, made only passing mention of what his aides believe are his signature accomplishments — the nation's economic rebound, the recent installation of Supreme Court Justice Amy Coney Barrett — in favor of a torrent of grievance and combativeness. He angrily decried the media's coverage of the campaign while complaining that he also was being treated unfairly by, in no particular order, China, the Electoral College system and rock singer Jon Bon Jovi.

Biden announced an unusual move to campaign on Election Day, saying he would head to Philadelphia and his native Scranton on Tuesday as part of a get-out-the-vote effort. His running mate, Sen. Kamala Harris, will visit Detroit, a heavily Black city in battleground Michigan, and both of their spouses will hit the road too. Trump, at least for now, was not scheduled to travel on Tuesday.

More than 93 million votes have already been cast, through early voting or mail-in ballots, which could lead to delays in tabulation. Trump has spent months claiming without evidence that the votes would be ripe for fraud and refusing to guarantee that he would honor the election result.

Trump also rallied in Scranton on Monday, underscoring the importance of the state's vote-rich northeast counties, and zeroed in on the state's process to count votes. He has used stark terms to threaten litigation to stop the tabulation of ballots arriving after Election Day — counting that is allowed with earlier postmarks in some states.

He has said that “we're going in with our lawyers” as soon as the polls close in Pennsylvania and on Monday spoke ominously about the Supreme Court decision to grant an extension to count the votes after Tuesday.

“They made a very dangerous situation, and I mean dangerous, physically dangerous, and they made it a very, very bad, they did a very bad thing for this state," Trump declared. He said of Pennsylvania's Democratic Gov. Tom Wolf, “Please don’t cheat because we’re all watching. We’re all watching you, Governor.”

There is already an appeal pending at the Supreme Court over the counting of absentee ballots in Pennsylvania that are received in the mail in the three days after the election.

The state’s top court ordered the extension, and the Supreme Court refused to block it, though conservative justices expressed interest in taking up the propriety of the three added days after the election. Those ballots are being kept separate in case the litigation goes forward. The issue could assume enormous importance if the late-arriving ballots could tip the outcome.

One of Biden’s top legal advisers Bob Bauer pushed back at Trump’s promise of mobilizing his lawyers after polls close to challenge certain ballots.

“It’s very telling that President Trump is focused not on his voters but on his lawyers, and his lawyers are not going to win the election for him,” Bauer said. “We are fully prepared for any legal hijinks of one kind or another. We’re not worried about it.”

And Harris said she believed Trump was simply blustering to “distract from the fact that he actually has no record to run on." She said "he wants to scare people, he wants to distract people, confuse people.”

Both Biden and Harris — and their spouses — were crisscrossing the state Monday.

Trump once led comfortably in neighboring Ohio. But Biden said he was returning to the state at the urging of Sen. Sherrod Brown other Ohio Democrats in Congress, suggesting a final, late visit could win.

Biden also has pushed into other formerly reliable Trump strongholds including Georgia, where the Democrats’ most popular surrogate, former President Barack Obama, campaigned Monday.

“I didn’t originally plan to come to Georgia. I told Michelle, I’m sorry, Baby, I got to go to Georgia. This is a big deal," said Obama, noting Democrats' hopes that they could deliver a knockout blow to Trump in the former GOP stronghold. “Georgia could be the state, Georgia could be the place.”

But even as Biden enjoyed strong poll numbers, the move to expand the map revived anxiety among Democrats scarred by Trump’s 2016 upset over Hillary Clinton, whose forays into red states may have contributed to losing longtime party strongholds. Biden planned a Pittsburgh drive-in event with Lady Gaga on Monday night, reminiscent of Clinton's rallying with Bruce Springsteen and Bon Jovi in Philadelphia on the eve of an election she was favored to win but didn't.

Short on campaign cash, Trump has been unable to compete with Biden over the airwaves and has relied on rallies to fire up his base. Those events, arguably the most striking political force of the past five years, could draw to a close Monday with stops in North Carolina, Pennsylvania, Wisconsin and two in Michigan. The last was set for Grand Rapids, the city where Trump held his finale four years ago.

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Lemire and Weissert reported from Washington. Miller reported from Charlotte, North Carolina. Associated Press writers Aamer Madhani in Washington, Kat Stafford in Detroit and Bill Barrow in Atlanta contributed.

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AP’s Advance Voting guide brings you the facts about voting early, by mail or absentee from each state: https://interactives.ap.org/advance-voting-2020/.