Pennsylvania’s highest court has thrown out a lower court’s order preventing the state certifying dozens of contests on its presidential election ballot in the latest Republican legal attempt to thwart Joe Biden’s victory in the battleground state.

The state’s Supreme Court, in a unanimous decision, threw out the three-day-old order on Saturday night, saying the underlying lawsuit was filed months after the expiration of a time limit in Pennsylvania’s mail-in voting law allowing for challenges to it.

Justices also remarked on the lawsuit’s staggering demand that an entire election be overturned.

“They have failed to allege that even a single mail-in ballot was fraudulently cast or counted,” Justice David Wecht wrote.

The state’s attorney-general, Democrat Josh Shapiro, called the decision “another win for democracy”.

US President Donald Trump and his lawyer Rudy Giuliani have repeatedly and baselessly claimed Democrats falsified mail-in ballots to steal the election from Mr Trump.

Mr Biden beat Mr Trump by more than 80,000 votes in Pennsylvania.

BREAKING: The Pennsylvania Supreme Court has DISMISSED the case brought by Rep. Kelly (R-PA) that sought to throw out all mail ballots cast in the November election.

Another loss for the Trump team.

— Brian Tyler Cohen (@briantylercohen) November 28, 2020

The week-old lawsuit, led by Republican US House member Mike Kelly of north-west Pennsylvania, challenged the state’s mail-in voting law as unconstitutional. It sought to throw out 2.5 million mail-in ballots – most for Democrats – or wipe out the November 3 election results and direct the state’s Republican-controlled legislature to pick its presidential electors.

The Trump campaign and its Republican allies have lost a flurry of legal challenges filed in state and federal courts in Pennsylvania.

On Friday, a federal appeals court in Philadelphia rejected the campaign’s latest effort to challenge the state’s election results.

Mr Trump’s lawyers vowed to appeal to the US Supreme Court despite the judges’ assessment the “campaign’s claims have no merit”.

-with AAP