LAS VEGAS - Republican U.S. Sen. John Ensign of Nevada, damaged politically and facing a Senate ethics investigation relating to an extramarital affair, said Monday that he won't seek reelection next year.

His decision could set off a free-for-all to fill a seat coveted by Democrats.

More than a dozen family members and supporters flanked Ensign during his announcement, including his wife, Darlene Ensign.

Ensign, 52, said he had fully intended to run until last week. "I just came to the conclusion that I just couldn't put my family though it," he said.

He said it was difficult to give up a job he loved, but "I have learned through the mistakes I have made that there are consequences to sin."

Last month the Senate Ethics Committee named a special counsel to investigate claims that Ensign violated ethics rules and federal law in the aftermath of his affair with Cynthia Hampton, a campaign aide married to Douglas Hampton, another Ensign aide.

Ensign acknowledged the affair in 2009 after Douglas Hampton threatened to go public. The senator later acknowledged that his parents had paid Cynthia and Douglas Hampton $96,000 after Douglas Hampton left his job in the senator's office. The Hamptons have suggested the payment was severance.

NEWS SERVICES