PHILADEPHIA (AP) — President Donald Trump and Democratic challenger Joe Biden have one last chance to make their case to voters in critical battleground states on Monday, the final full day of a campaign that has laid bare their dramatically different visions for tackling the nation’s pressing problems and for the office of the presidency itself.

The candidates are seeking to lead a nation at a crossroads, gripped by a historic pandemic that is raging anew in nearly every corner of the country and a reckoning over race. More than 93 million people have already voted and it could take longer than usual for elections officials to process the historic surge in early and mail-in ballots.

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 while also threatening legal action to stop vote counting in some crucial states, including Pennsylvania.

The Republican president's final day has him sprinting through five rallies, from North Carolina to Wisconsin. Biden, meanwhile, was devoting most of his time to Pennsylvania, where a win would leave Trump with an exceedingly narrow path. Biden was also dipping into Ohio, a show of confidence in a state where Trump won by 8 percentage points four years ago.

Heading into the closing 24 hours, Trump and Biden each painted the other as unfit for office and described the next four years in near apocalyptic terms if the other were to win.

“The Biden plan will turn America into a prison state locking you down while letting the far-left rioters roam free to loot and burn,” Trump thundered Sunday at a rally in Iowa, one of the five he held in battleground states.

Biden said America was on the verge of putting “an end to a presidency that’s fanned the flames of hate.”

“When America is heard, I believe the message is going to be clear: It’s time for Donald Trump to pack his bags and go home,” Biden said in Philadelphia, the biggest city in a state that could decide the presidency.

As the candidates close out the campaign, the pandemic, which has killed more than 231,000 people nationwide and caused nearly 20 million to lose jobs, reached a new peak in infection rates, threatening yet another blow to lives and livelihoods of voters.

The election caps an extraordinary year that began with Trump’s impeachment, the near collapse of Biden’s candidacy during the crowded Democratic primary and then was fully reshaped by the coronavirus outbreak.

A record number of votes have already been cast, through early voting or mail-in ballots, which could lead to delays in their tabulation. Trump has spent months claiming without evidence that the votes would be ripe for fraud while refusing to guarantee that he would honor the election result.

In the starkest terms yet, Trump on Sunday threatened litigation to stop the tabulation of ballots arriving after Election Day. As soon as polls closed in battlegrounds such as Pennsylvania, Trump said, “we’re going in with our lawyers.”

It was unclear precisely what Trump meant. 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.

Under the shadow of possible legal battles, Pennsylvania loomed as most important battleground.

For Biden, who lives in neighboring Delaware, Pennsylvania has long been the focus of his campaign, a bulwark to block Trump from securing the electoral votes needed for reelection. Both he and his running mate, Sen. Kamala Harris, and their spouses will crisscross the state Monday — hoping to deliver a knockout blow to Trump without potential Pennsylvania legal challenges.

Trump once led comfortably in Ohio. Biden's trip there comes after his ticket’s pushes into other formerly reliable Trump strongholds including Georgia, where the Democrats’ most popular surrogate, former President Barack Obama, was campaigning Monday.

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 Jon 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 dominant political force of the last five years, could draw to a close Monday with stops in North Carolina, Pennsylvania, Wisconsin and two in Michigan. The last will be in Grand Rapids, the same city where Trump held his finale four years ago.

Trump is focusing his last rounds of stops on states he won four years ago, playing defense in a campaign that has become a referendum on his handling of the pandemic. Both parties say the election holds outsize importance.

Adam Jentleson, a progressive strategist and former top aide to ex-Senate Democratic leader Harry Reid of Nevada, said the election will be the most important of the country’s collective lifetime because it “is about restoring the basic structure of a functioning, multiracial democracy that can be responsive to the will of its people.”

Republican strategist Alice Stewart said the pandemic, the economy and race relations in America have all coincided in unprecedented ways, but that Election Day’s outcome won’t bring an immediate fix no matter what happens.

“If 2020 is the most consequential election of our lifetime, heaven help us for 2024,” Stewart said. “I’m calling Noah and we'll start building the ark.”

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Lemire and Weissert reported from Washington. Miller reported from Charlotte. Associated Press writers Kat Stafford in Detroit and Bill Barrow in Atlanta.

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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/.