Joe Miller, a Republican candidate backed by the Tea Party, has conceded defeat to Lisa Murkowski in Alaska's US Senate election.
The move ends a protracted legal challenge that Mr Miller mounted following the election on 2 November.
Authorities certified Ms Murkowski's victory on Thursday, but Mr Miller could have appealed.
Ms Murkowski lost the Republican nomination in August to Mr Miller, but she ran a write-in campaign.
This involves voters adding a candidate's name to the ballot paper as they vote.
Mr Miller had challenged the validity of some ballots, saying those on which her name was misspelled should not be counted.
Ms Murkowski is the first Senate candidate to be elected in a write-in campaign since Strom Thurmond in 1954.