Washington DC - The 2020 presidential election saw dozens of legal challenges by the losing candidate, Republican Donald Trump, summarily tossed out by the courts.

This year's nail-biter of a White House race between the former president and Democratic nominee Kamala Harris has seen a deluge of lawsuits from both parties even before Election Day.

Democrats claim Republicans are setting the stage for Trump to contest the results if he loses and declare victory anyway – as he did four years ago.

"Trump uses litigation to create a grievance structure that will allow him to claim he is a victim when he loses fair and square," Marc Elias, a top Democratic Party election lawyer, said on X.

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Republicans say they are bringing the suits in the name of "election integrity," with Trump alleging that the only way Harris can win on Tuesday is if Democrats "cheat."

"I know, better than most, the rampant Cheating and Skullduggery that has taken place by the Democrats in the 2020 Presidential Election," he said in a Truth Social post.

The 78-year-old Trump has never conceded the election he lost to Joe Biden, and a defeat this time could pave the way for the former president to be put on trial on federal and state charges of conspiring to overturn the 2020 results.

The Republican National Committee (RNC), which is co-chaired by Trump's daughter-in-law Lara, has filed more than 130 cases, mostly focused on the seven swing states that could decide the election: Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin.

The suits filed by the RNC and allied groups have targeted ballot-counting procedures, voting machines, voter registration, absentee ballots, the certification of results and a host of other issues.

Republicans have been particularly focused on preventing non-US citizens from voting, wildly exaggerating what watchdog groups say is a very rare occurrence.

In several states, they have targeted the rules for mail-in ballots, which Democrats have historically used at far greater rates than Republicans.

Democrats have filed dozens of suits of their own, seeking to protect mail-in voting, overseas ballots and increase the number of ballot drop boxes. They have recruited an army of lawyers to litigate pre- and post-election disputes.

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David Becker, executive director of the Center for Election Innovation and Research, said many of the Republican pre-election lawsuits, most of which have been dismissed, are not designed to legitimately clarify voting rules but to "set the stage for claims the election was stolen."

"We're going to see these claims revived, depending on the outcome," Becker said during a panel held by the advocacy group Free Press.

The Republican legal efforts are better organized this time around than four years ago, when they were haphazardly led by Trump's personal attorney Rudy Giuliani.

Giuliani, the former New York mayor, ended up being indicted in Georgia and Arizona for his efforts to subvert the election results and was ordered to cough up nearly $150 million for defaming two poll workers.

"In 2020, Trump had a motley collection of attorneys, many of whom were as short on legal acumen as they were long on wild conspiracy theories," said Donald Nieman, a Binghamton University history professor.

Some of the most notable pre-election litigation has cropped up in Georgia, where Biden defeated Trump by less than 12,000 votes in 2020 and Trump-allied election board members sought to enforce new rules.

Georgia courts blocked the changes, one of which would have required a manual hand count of ballots and another that would have given board members the power to refuse to certify the results.

Derek Muller, who teaches election law at the University of Notre Dame, said the number of votes potentially affected by each pre-election case is "very small" – 1,000 or 2,000 voters or ballots.

At the same time, "if the election is extremely close – and in 2000 in Florida it was decided by 537 votes – then everything matters," Muller said in a reference to Republican George W. Bush's winning margin over Democrat Al Gore.

The conservative-dominated Supreme Court controversially settled a recount dispute in the 2000 election in Bush's favor and could be called upon to play a role again this time.

The top court has mostly stayed on the sidelines of the current campaign, but it did step in Wednesday, allowing the Republican-led state of Virginia to purge about 1,600 people from voter rolls for allegedly not being US citizens.

It was a 6-3 vote, with the three liberal justices dissenting.