Less than 24 hours until Election Day, the Trump and Biden campaigns are winding down their rigorous battles fought via ad campaigns, debates and rallies, while digging in for a whole new war, this one to be waged in courtrooms.

Both sides have amassed their battalions of attorneys, and it appears that they will not wait long to engage.

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“We're going to go in [the] night of, as soon as that election is over, we're going in with our lawyers,” President Trump told reporters Sunday, referring to litigation over whether ballots in swing states such as Pennsylvania and North Carolina should be counted if they arrive in the mail after Election Day.

"I don't think it's fair that we have to wait a long period of time after the election. Should've gotten their ballots in a long time before that. Could've gotten their ballots in a month ago. I think it's a ridiculous decision,” the president said, referring to the Supreme Court’s decision not to block state court orders that allowed extensions.

Pennsylvania Secretary of State Kathy Boockvar said Sunday that she expects the “overwhelming majority” of ballots to be tallied in a few days’ time, but whether all of those votes will ultimately count will depend on how the ongoing court case plays out. She confirmed that ballots received after Election Day will be segregated from the rest, just in case they are ruled invalid.

To handle this and other legal matters, Trump’s campaign has formed what it has called “Lawyers for Trump,” a coalition to “protect the integrity” of the election.

The coalition is being led by Texas Attorney General Ken Paxton and Arkansas Attorney General Leslie Rutledge, as well as California Committeewoman Harmeet Dhillon and former Deputy White House Counsel Stefan Passantino. The group includes prominent Trump-allied attorneys like former Florida Attorney General Pam Bondi, former Attorney General Ed Meese and the president's personal attorney Rudy Giuliani.

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The Lawyers for Trump coalition comes as part of the joint Republican National Committee and Trump campaign's "Protect the Vote" effort, which has warned for months that "Democrats are trying to use coronavirus and the courts to legalize ballot harvesting, implement a nationwide mail-in ballot system, and eliminate nearly every safeguard in our elections."

John Hansberry, with the Philadelphia City Commissioners office, demonstrates an extraction machine at the city's mail-in ballot sorting and counting center in preparation for the 2020 General Election in the United States, Monday, Oct. 26, 2020, in Philadelphia. (AP Photo/Matt Slocum)

Trump campaign general counsel Matthew Morgan told Fox News in October that the campaign is urging active and retired attorneys and even law students to volunteer in their nationwide efforts.

“Democrats are working to shred election integrity measures one state at a time, and there’s no question they’ll continue their shenanigans from now to November and beyond,” Morgan told Fox News. “The Trump campaign is fighting to ensure every valid ballot across America counts – once.”

The Biden campaign, meanwhile, has been quietly building a massive "election protection program," including former Attorney General Eric Holder and hundreds of other lawyers in preparation for a legal battle in the event of a contested election.

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The campaign said this team includes Bob Bauer, who has signed on full-time as a senior campaign adviser while on leave from the faculty of NYU Law School. Bauer, who served as general counsel to the Obama-Biden campaigns in 2008 and 2012 and co-chair of former President Obama's Presidential Commission on Election Administration, will work alongside the campaign’s general counsel, Dana Remus.

Remus has oversight of the campaign’s day-to-day legal operations, and will oversee the wide-ranging team of lawyers to address voter protection.

A national team for special litigation features former Solicitors General Donald Verrilli and Walter Dellinger, and a team at the law firm Perkins Coie, which is headed by Marc Elias. Perkins Coie played a key role in Hillary Clinton’s 2016 campaign, and it was Elias who Fusion GPS, the firm that conducted opposition research that ultimately included Christopher Steele’s dossier.

The Biden team's lawyers will focus state-by-state on protecting voter access to the polls and a “fair and accurate vote count.”

Democrats and Republicans are each claiming the other side is looking to rig the 2020 election in their favor, with accusations largely stemming from mail-in voting, which is being utilized to an unprecedented degree as a precaution to allow voters to avoid crowds during the coronavirus pandemic.

Democrats claim that by opposing special measures to accommodate large-scale mail-in voting, Republicans are looking to disenfranchise American voters. As long as they submit their votes by Election Day, their votes should count, even if they do not arrive until several days later, they argue.

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Boockvar noted that it would be nothing new to have ballots counted after Election Day, as military votes are normally not received until days later. States have different deadlines for when service members’ ballots must be received. According to the Federal Voting Assistance Program, Pennsylvania ballots must be signed by voters by 11:59 p.m. Monday, the day before Election Day, and arrive no later than 5 p.m. on the seventh day after Election Day.

For civilian voters in Pennsylvania, the law had been that the state Board of Elections ballots must be received by 8 p.m. on Election Day. Democrats challenged this, seeking an injunction to allow ballots to be accepted up to three days later, as long as they are postmarked by Nov. 3. They claimed that this was necessary because during this year’s primary election, “at least tens of thousands of voters ultimately did not receive their ballots with enough time to return them by the close of the polls on Election Day.”

The State Supreme Court granted the extension, leading Republicans to seek review from the U.S. Supreme Court, arguing that it is up to the legislature, not the court, to set election rules. The U.S. Supreme Court has yet to take up the case, but they denied a request to put the state court’s ruling on hold.

A similar case is being litigated in North Carolina, where the deadline has been pushed to a week after Election Day.

Republicans have claimed that Democrats are trying to change existing rules for their benefit. Trump has claimed that large-scale mail-in voting is not as secure as in-person, and leaves the system open to fraud. While clear cases of fraudulent behavior have yet to be proven thus far, the system has shown to be problematic in some instances, such as when more than 100 undelivered absentee ballots were found in a Kentucky dumpster.

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While Pennsylvania sided with Democrats, courts in states like Maine have denied pushes to extend ballot deadlines.

“A judicial declaration that the statutory deadline is not really a deadline at all, and can be altered and extended for a week or more, risks undermining voter confidence that the law means what it says and that the voting and the election are over,” Maine Superior Court Justice William Stokes wrote in an order.

Fox News’ Brooke Singman contributed to this report.