An Arizona judge on Saturday dismissed a lawsuit brought by Republican candidate Kari Lake, a Donald Trump loyalist who sought to overturn her unsuccessful bid to become the south-western state's governor.
The court found no "clear and convincing evidence of misconduct" that would have affected the outcome of the November election as Ms Lake alleged, Judge Peter Thompson said in his decision.
Ms Lake, a 53-year-old former TV news anchorwoman, tweeted on Saturday that "for the sake of restoring faith and honesty in our elections, I will appeal his ruling".
After losing to Democrat Katie Hobbs by a margin of 17,117 votes, Ms Lake claimed that problems with ballot printing in Maricopa County, Arizona's most populous county which includes its capital, were intentional and aimed at her defeat.
Mr Thompson said the court could not accept speculation or conjecture in lieu of clear and convincing evidence, while upholding Ms Hobbs's victory.
Ms Lake supporters had seized upon minor problems with vote tabulation machines in Maricopa, home to America's fifth biggest city, Phoenix, which left some people standing in queues during the November vote.
Officials had insisted that no legitimate vote would be excluded, and mounted a well-organised social media campaign to push back at falsehoods circulating online.
Arizona has been under intense scrutiny for two years since Joe Biden eked out a narrow win in the state over Mr Trump, president at the time.
Maricopa County became ground zero for election deniers, who made unfounded claims about ballot stuffing, despite repeated investigations that turned up no evidence of wrongdoing.
Ms Lake made denial of Mr Biden's 2020 presidential election win a key tenet of her campaign, and said that she would not have validated his victory if she had been in the governor's mansion at the time.
She was thought of as a leading light in the movement, and Republican Party insiders — as well as media pundits ― have noted that regardless of the Arizona result, she could be well placed for a spot on a future White House ticket.