A judge in Pennsylvania has dismissed a lawsuit from the Trump campaign that sought to invalidate millions of mail-in votes in the battleground state.
Judge Matthew Brann said the suit, which rested on allegations of irregularities, was “without merit”.
The move paves the way for Pennsylvania to next week certify Joe Biden’s win – he leads by more than 80,000 votes.
It is the latest blow to Donald Trump, who is trying to overturn his loss in the 3 November presidential election.
He has refused to concede and made allegations of widespread electoral fraud, without providing any evidence.
The lack of a concession has upended the process that normally follows a US election.
Mr Biden is projected to defeat President Trump 306 to 232 in the US electoral college, which determines who becomes president – far above the 270 he needs to win.
The Trump campaign has lost a slew of lawsuits contesting results from the election, and their latest efforts focus on stopping the swing states that handed Mr Biden his win certifying the results – an essential step for the Democrat to be formally declared victor.
Pennsylvania judge gives scathing verdict
In the ruling Judge Brann wrote that the Trump campaign had tried to “disenfranchise almost seven million voters”.
He said his “court has been presented with strained legal arguments without merit and speculative accusations”.
“In the United States of America, this cannot justify the disenfranchisement of a single voter, let alone all the voters of its sixth most populated state,” the judge wrote.
The Trump campaign argued that the state had violated the US Constitution’s guarantee of equal protection under the law as some, Democratic-run counties allowed voters to fix errors on their ballots while Republican-run counties did not.
But in his ruling Judge Brann dismissed the claim, saying “like Frankenstein’s Monster” it had been “haphazardly stitched together”. He said even if it was the basis for a case then the Trump campaign’s solution went too far.
Few Republicans have called on the president to concede, but following the judge’s ruling Republican Pennsylvania Senator Pat Toomey said Mr Trump had exhausted all legal options in the state and urged him to accept the result.
President Trump’s personal lawyer, Rudy Giuliani, said in a statement he would appeal against the ruling: “Today’s decision turns out to help us in our strategy to get expeditiously to the US Supreme Court.”