Democratic candidate Katie Hobbs has defeated Republican Kari Lake in Arizona's race for governor, CBS News has projected.
The result is a rebuke of Ms Lake, who has peddled the false claim that Donald Trump won the 2020 US election.
In her victory statement, Ms Hobbs said that "in this moment of division" she would work for everyone in the state.
Ms Lake appeared to suggest that the result was incorrect, and that some votes for her had not been counted.
Elsewhere, almost a week after votes were cast, the race to control the House of Representatives remains tight.
Republicans must win at least 218 seats to claim a majority in the House of Representatives, a prospect that has sharply narrowed.
The party has currently won 215 seats while Democrats have won 211, according to race projections from CBS News.
READ ALSO: US midterms: Democrats retain control of Senate after key Nevada victory
In a midterm election that has further highlighted the stark partisan divisions in America, Ms Hobbs called for unity, saying she would work for those Arizonans who did not vote for her.
"Even in this moment of division, I believe there is so much more that connects us," she said.
Her opponent, Ms Lake - who was endorsed by Mr Trump - told the BBC during campaigning that the former president should not need to run again in the 2024 election because "he won the last election". She predicted he would "come back with a vengeance".
There is no evidence that the 2020 election was stolen.
Ms Lake's defeat sees her join the ranks of pre-eminent Trump-backed election deniers who lost last week. But a BBC News tally of results found at least 125 election deniers have won races for the House, Senate and governorships.
The midterm elections are also for Congress, including all seats in the House of Representatives and one third of those in the Senate.
The Biden administration had feared that a loss of power in Congress would bring the president's agenda to a halt. However, the Democrats have retained control of the Senate, and the House has not yet been called.
If the two parties split control of Washington, Democrats will "maintain our positions" but voters should not "expect much of anything", President Biden said on Monday.
Speaking to reporters in Indonesia, where he is attending the G20 summit, Mr Biden said the results had "sent a very strong message around the world that the United States is ready to play" and wants to remain "fully engaged in the world".
He noted there was "a strong rejection" of election denialism, political violence and voter intimidation. But he warned that, without a majority in the House, Democrats would be unable to codify abortion rights through legislation, a key priority for liberal voters.
Out of the 11 House races that still remain to be called, most are in western and southwestern states, including California and Arizona.
BBC