A six-month battle over a North Carolina Supreme Court seat ended on Wednesday when the Republican challenger, who had embarked on an extraordinary effort to throw out thousands of votes, conceded the race.

The challenger, Judge Jefferson Griffin, said in a statement that he would not appeal a federal court ruling issued on Monday that ordered the state elections board to certify the victory for the Democratic incumbent, Justice Allison Riggs.

“While I do not fully agree with the District Court’s analysis, I respect the court’s holding — just as I have respected every judicial tribunal that has heard this case,” Mr. Griffin said. “I will not appeal the court’s decision.”

Two recounts had affirmed that Justice Riggs won the race by a margin of 734 votes out of the more than 5.5 million ballots that were cast. The results of the race are the last in the nation to be certified from the 2024 election.

This is a developing story. Check back for updates.