Nevada Republican John Ensign, who admitted having an extramarital affair with a campaign staff member, has announced that he will resign from the US Senate on 3 May.
Mr Ensign, 52, announced last month that he would not seek re-election in 2012. He had been facing a Senate ethics probe stemming from the extramarital affair.
Mr Ensign admitted to having an affair in 2008 with Cynthia Hampton, who worked for his campaign, and whose husband, Douglas, was an aide. The Senate ethics investigation focused in part on $96,000 Mr Ensign's parents gave to the Hamptons, which Mr Ensign's attorney has characterized as a gift.