Updated 7:22 p.m.In a statement Tuesday night, Senate GOP Policy Committee Chairman John Ensign (Nev.) acknowledged an extramarital affair with a married woman who previously worked as a campaign staffer for him in the 2008 cycle.Last year I had an affair. I violated the vows of my marriage. It is the worst thing I have ever done in my life. If there was ever anything in my life that I could take back, this would be it, Ensign said in a statement from his office.Ensign declined to identify the woman but said she and her husband both worked for him. The Associated Press reported the affair took place from December 2007 to August 2008 with a campaign staffer who was married to someone who worked in Ensigns Capitol Hill office.Our families were close. That closeness put me into situations which led to my inappropriate behavior. We caused deep pain to both families and for that I am sorry, he said.Ensign, who once demanded the resignation of former Sen. Larry Craig (R-Idaho) after it was revealed that he had pleaded guilty to charges of disorderly conduct in a airport mens restroom, gave no indication that he had any plans to step down from his Senate duties over the matter.I am committed to my service in the United States Senate and my work on behalf of the people of NV, the statement said. Ensign, who was elected to the Senate in 2000, chaired the National Republican Senatorial Committee during the 2008 cycle. More recently, he has been viewed as a possible contender for president in 2012.