Senator John Ensign, Republican of Nevada, on Tuesday admitted that he had an extramarital affair with a member of his campaign staff.

Mr. Ensign led the Republicans’ campaign efforts in 2008 and had been contemplating a run for president in 2012

The woman’s husband was a member of Mr. Ensign’s official Senate staff

Mr. Ensign, 51, is married and has three children. During college at Colorado State University, he became a born-again Christian and he and his wife, Darlene, were active in the Promise Seekers, an evangelical group

Ensign, a member of the Senate GOP leadership, flew back to his native Las Vegas today in anticipation of the public announcement, sources said, missing a vote considered key to the Nevada tourist industry.

In February 2002, Ensign took an unexplained two week leave of absence from the Senate citing "personal reasons."

Ensign

demanding the resignation of Larry Craig in September 2007