In the request on Tuesday to the US Supreme Court, Republican US Representative Mike Kelly of northwestern Pennsylvania and the other plaintiffs are asking the court to prevent the state from certifying any contests from the November 3 election, and undo any certifications already made, such as Biden’s victory.

They maintain that Pennsylvania’s expansive vote-by-mail law is unconstitutional because it required a constitutional amendment to authorise its provisions.

Biden beat President Donald Trump by more than 80,000 votes in Pennsylvania, a state Trump had won in 2016.

Pennsylvania’s Supreme Court on Saturday night threw out the lawsuit, including an order by a lower court judge blocking the certification of any uncertified races.

Justices cited the law’s 180-day time limit on filing legal challenges to its provisions, as well as the staggering demand that an entire election be overturned retroactively.

In the state’s courts, Kelly and the other Republican plaintiffs had sought to either throw out the 2.5 million mail-in ballots submitted under the law – most of them by Democrats – or to wipe out the election results and direct the state’s Republican-controlled Legislature to pick Pennsylvania’s presidential electors.

Trump also filed a lawsuit in Wisconsin seeking to disqualify more than 221,000 ballots in the state’s two most Democratic counties, a long-shot attempt to overturn Biden’s win in a battleground state he lost by nearly 20,700 votes.

Trump filed on Tuesday, the day after Democratic Governor Tony Evers and the chairwoman of the Wisconsin Elections Commission certified Biden as the winner of the state’s 10 Electoral College votes.

Trump asked the Wisconsin Supreme Court to take the case directly, rather than have it start in a lower court, and order Evers to withdraw the certification.

The Wisconsin Supreme Court gave Evers until 8:30pm on Tuesday to respond to the lawsuit, an unusually tight deadline that speaks to how quickly the court is likely to decide the case.

The state’s highest court, controlled 4-3 by conservatives, also is considering whether to hear two other lawsuits filed by conservatives seeking to invalidate ballots cast during the presidential election.

Separately, two Wisconsin Republicans filed a new federal lawsuit on Tuesday that mirrors some of Trump’s claims and asks a judge to declare him the winner in Wisconsin.

Trump’s lawsuit repeats many false claims he made during a recount of votes in Milwaukee and Dane counties that large swaths of absentee votes were illegally cast.

Local officials rejected his claims during the recount, and Trump is challenging procedures that have been in place for years and never been found to be illegal.

Trump is not challenging any ballots cast in conservative counties he won.

Biden campaign spokesman Nate Evans called the lawsuit “completely baseless and not rooted in facts on the ground”.

Democratic Governor Tony Evers said it was “without merit”.

Trump’s Wisconsin lawyer, Jim Troupis, said in a statement that voters “deserve election processes with uniform enforcement of the law, plain and simple”.

Similar Trump campaign lawsuits have failed in other battleground states.

Trump is running out of time to have his legal cases heard. The Electoral College is scheduled to meet on December 14 and Congress is to count the votes on January 6.

-with AAP