US District Court Judge Matthew Brann ruled that Trump's campaign had failed to demonstrate there had been widespread voting fraud in the November 3 election, which Trump lost to Democrat Joe Biden.
"This Court has been presented with strained legal arguments without merit and speculative accusations," Brann wrote. Brann added that he "has no authority to take away the right to vote of even a single person, let alone millions of citizens".
The lawsuit, spearheaded by Trump's personal lawyer Rudy Giuliani, sought to stop officials from certifying Biden's victory in the state, arguing that some counties wrongly allowed voters to fix errors on their mail ballots.
Giuliani, who made his first courtroom appearance in 30 years for a hearing in the case on Tuesday, did not immediately respond to a request for comment. The Biden and Trump campaigns also did not immediately respond to queries.
Giuliani and other Trump lawyers floated a variety of conspiracy theories at a news conference on Thursday as they alleged that the election was marred by widespread voter fraud.
But they have had little success in court.
Trump and his allies have now won two election-related cases and lost 34, according to Democratic election lawyer Marc Elias.
Democrats said Saturday's scathing verdict was further proof that those charges are false. (Reuters)