Without comment, the nation's highest court refused to call into question the certification process in Pennsylvania, where Joe Biden's 80,000-strong victory over Donald Trump has already been declared.
The US Supreme Court has rejected the Republicans' last bid to reverse President-elect Joe Biden's victory in Pennsylvania. But Republican representatives say even now that this is not over yet.
Donald Trump and his legal teams have been contesting official results from the November 3 election, but the legal challenges have systematically been thrown out of state courts. Meanwhile, the outgoing president has continued to repeat claims of widespread fraud, evidence-free.
This time even the nation's highest tribunal with its conservative majority was unimpressed.
The Supreme Court, without comment, refused to call into question the certification process in Pennsylvania on Tuesday. Democratic governor, Tom Wolf, has already certified Biden's 80,000-strong victory over Trump.
The state's 20 electors are to meet on 14 December to cast their votes for Biden.
In any case, Biden won 306 electoral votes, so even if Pennsylvania's results had been in doubt, he still would have more than the 270 electoral votes needed to become president.
The court's decision not to intervene came in a lawsuit led by Republican U.S. representative Mike Kelly of northeastern Pennsylvania, and Republican congressional candidate - and Trump favourite - Sean Parnell, who lost to Pittsburgh-area U.S. representative Conor Lamb, (Democrat).
The state's high court said the plaintiffs waited too long to file the challenge and noted the Republicans' staggering demand that an entire election be overturned retroactively.
Republicans had pleaded with the justices to intervene immediately after the state Supreme Court turned away their case last week.
The Republicans argue that Pennsylvania's expansive vote-by-mail law is unconstitutional because it required a constitutional amendment to authorise its provisions. Just one Republican state lawmaker voted against its passage last year in Pennsylvania's Republican-controlled Legislature.
"Even Trump appointees & Republicans saw this for what it was: a charade," Lamb said on Twitter.
In court filings, lawyers for Pennsylvania and governor Tom Wolf (Democrat) had called the lawsuit's claims "fundamentally frivolous" and its request "one of the most dramatic, disruptive invocations of judicial power in the history of the Republic."
"No court has ever issued an order nullifying a governor's certification of presidential election results," they wrote.
Republican U.S. senator Ted Cruz of Texas had offered to argue the case, if the high court took it on. "I’m disappointed the Court decided not to hear the case challenging the election results in Pennsylvania," Cruz said in a tweet on Wednesday. "The anger and division we see across the Nation needs resolution."
'By no way is this over': What will the Republicans do next?
Having lost the request for the court to intervene immediately, Greg Teufel, a lawyer for Kelly and Parnell, said he will file a separate request to ask the court to consider the case on its underlying merits on an expedited basis.
Hopes of immediate intervention concerning the 3 November election have been "substantially dimmed" by the court's action on Tuesday, Teufel said.
"But by no way is this over," Kelly told Fox News.
Meanwhile, President-elect Joe Biden is looking ahead to inauguration day in January,
Biden beat Trump by more than 80,000 votes in Pennsylvania, a state Trump had won in 2016. Most mail-in ballots were submitted by Democrats.
In the underlying lawsuit, Kelly, Parnell and the other Republican plaintiffs had sought to either throw out the 2.5 million mail-in ballots submitted under the law, or to wipe out the election results and direct the state's Republican-controlled Legislature to pick Pennsylvania's presidential electors.