Just two weeks after taking the first steps toward a 2012 presidential bid, conservative Republican Sen. John Ensign of Nevada is admitting to an extramarital affair last year with a campaign aide.

Ensign, a rising star in conservative circles and Nevada’s most popular Republican, disclosed the affair at a hastily arranged news conference here Thursday, shattering his prospects for heading his party’s ticket three years from now and jarring a state already dealing with a scandal involving its GOP governor.

"Last year I had an affair. I violated the vows of my marriage," Ensign told reporters, refusing to take any questions. "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, 51, belongs to the men’s Christian ministry Promise Keepers, and has championed causes pushed by the GOP’s conservative religious base.

Earlier this month, he went to Iowa, home to the nation’s first presidential precinct caucuses, to speak as part of a conservative lecture series designed to define the GOP after its shattering defeat in last year’s presidential and congressional elections. Aides said the visit was about staking out a leadership position within the GOP.

"This really doesn’t help a Republican Party that has tried to run as a party of family values," said Chuck Muth, a self-described conservative-libertarian activist. "It absolutely makes the party look hugely hypocritical."

Eric Herzik, a political science professor at the University of Nevada-Reno, called Ensign’s announcement "another shot in the gut to Nevada Republicans."

"The party is in disarray and Ensign was at least a bright spot. He was respected," Herzik said.

Nevada Gov. Jim Gibbons is going through a messy divorce and has been accused by his wife, Dawn Gibbons, of infidelity.

Ensign did not disclose what prompted his decision to declare his infidelity. He made it clear he doesn’t intend to resign. He would not mention the name of the campaign aide involved in the affair but described her and her husband as good friends.

"Our families were close," a weary-looking Ensign said. "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."

Ensign’s spokesman, Tory Mazzola, said the affair took place between December 2007 and August 2008 with a campaign staffer who was married to an employee in Ensign’s Senate office. She worked at Ensign for Senate and at his Battle Born Political Action Committee from December 2006 to May 2008. Neither the women nor her husband have worked for Ensign since then, Mazzola said.

Ensign’s wife, Darlene, also issued a statement about the affair but did not appear with him at the news conference.

"Since we found out last year we have worked through the situation and we have come to a reconciliation. This has been difficult on both families. With the help of our family and close friends our marriage has become stronger," Mrs. Ensign said.

The Ensigns have three children.

In 2002, Ensign missed several public appearances and dropped official business for about two weeks to deal with what his aides then described as a family matter. A person familiar with that episode, speaking on condition of anonymity because of the sensitivity of the matter, said Tuesday the absence followed an earlier affair.

Ensign skipped Tuesday’s Senate session, missing a vote on legislation relating to the travel industry, an important part of his state’s economy. He was not expected to return to the Capitol until at least Thursday. His announcement drew no public reaction from Sen. Mitch McConnell, R-Ky., the party’s leader in the Senate, or other members of the leadership.

Ensign’s admission complicates GOP efforts to unseat Democratic Majority Leader Harry Reid, also from Nevada, in next year’s midterm congressional elections.

A recent poll showed that more voters were prepared to vote against Reid than for him. Republicans nationally and in the state have made his defeat a priority but have been unable to find a strong challenger so far in the face of a large campaign fund that Reid has built up.

"Reid is not beloved in this state. His public approval ratings have always lagged, … but now, compared to our governor, and with Ensign’s problems, it makes Reid look that much more substantial," Herzik said.

Nevada GOP chairwoman Sue Lowden, said Ensign’s admission "has no impact on the party or our plans for 2010. It’s a personal matter for the Ensign family and that’s it."

Ensign was elected to the House in the Republican landslide of 1994. He won his Senate seat in 2000 after losing his first Senate bid two years earlier in a bitter contest with Reid. Since then, the two have worked closely on Nevada issues and they have an agreement not to criticize each other publicly.

"Senator Reid’s thoughts are with Senator Ensign and his family at this time," said Reid spokesman Jon Summers.

After his election in 2000, Ensign quickly rose through the GOP ranks. He chaired the GOP’s Senate campaign operation in 2007 and 2008, and last year was named chairman of the Republican Policy Committee, the No. 4 position in the party’s Senate leadership. The committee coordinates the GOP’s legislative efforts in the Senate.

Ensign had been highly critical of former Sen. Larry Craig, R-Idaho, who served in Congress for a quarter-century, after Craig’s arrest in an airport bathroom sex sting. Ensign stopped short of urging Craig to resign but suggested strongly that he should.

"I wouldn’t put myself hopefully in that kind of position, but if I was in a position like that, that’s what I would do," Ensign said. "He’s going to have to answer that for himself." In the end, Craig served out his term.


Freking reported from Washington. Associated Press reporter Brendan Riley in Carson City, Nev., contributed to this report.