By Greg Vadala and Bart Jansen, CQ Staff

Sen. John Ensign of Nevada acknowledged Tuesday he had an extramarital affair with a woman on his campaign staff married to a member of Ensign’s Senate staff.

“It is the worst thing I have ever done in my life,” Ensign said in a statement he read to reporters in Las Vegas. “If there was ever anything in my life that I could take back, this would be it.”

The affair took place between December 2007 and August 2008, according to an Ensign aide who asked not to be identified. Neither the woman nor her husband has worked for the Republican senator since May 2008, the aide said.

Ensign did not name the woman in his statement, but said she and her husband were close friends of his own family. “That closeness put me into situations which led to my inappropriate behavior,” he said.

The senator said in his statement that his wife, Darlene, has forgiven him and that after counseling their marriage is “stronger than ever.” Darlene Ensign agreed with that assessment in a statement to the Associated Press.

Ensign, 51, a veterinarian, father of three and former House member (1995-99), was elected to the Senate in 2000 and has been viewed as a rising star in Republican politics. He was chairman of the Senate Republicans’ campaign arm in the last election cycle and is now chairman of the Senate Republican Policy Committee. He made a trip to Iowa earlier this month, fueling speculation he was considering a presidential candidacy.

Senate Majority Leader Harry Reid , a fellow Nevadan who has worked closely with his Republican colleague, told reporters: “I don’t know the details. I talked with him today. Of course, he’s my friend. This is a private, family matter. I just hope that Darlene and he work things out.”

Ensign came to Congress as part of the Republican takeover of the House in 1995. He left the House to challenge Reid in 1998, losing by 428 votes. Two years later, Ensign won the Senate seat left open by the retirement of Democrat Richard H. Bryan.