LAS VEGAS â Sen. John Ensign of Nevada, a leading Republican mentioned as a potential presidential candidate, admitted Tuesday he had an extramarital affair with a woman who was a member of his campaign staff. "Last year I had an affair. I violated the vows of my marriage," Ensign said at a brief news conference in his home state. "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." An aide in Ensign's office 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. Neither has worked for the senator since May 2008. The aide spoke on condition of anonymity because he was not authorized to discuss the developments. Ensign said he would not mention the name of the female campaign aide involved in the affair. He described the woman 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 made it clear he did not plan to resign. Ensign did not participate earlier Tuesday in a vote concerning the ailing travel industry, an unusual absence considering the topic's relevance in his home state. Ensign's wife, Darlene, also released a statement about the affair. "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. Ensign was first elected to the Senate in 2000 and has been an influential conservative voice within that chamber. Last year, his GOP colleagues picked him to serve as chairman of the Republican Policy Committee, moving him to the No. 4 position in leadership. The committee coordinates the GOP's legislative efforts in the Senate. Previously, Ensign ran the Republican Senate campaign operations. Last month, Ensign traveled to Iowa for a speech organized by a conservative advocacy group, sparking speculation that he had an interest in possibly running for president. Aides said the visit was about staking out a leadership position within the GOP. Ensign has been a rising star among conservatives, speaking out against President Barack Obama's stimulus package, statehood for the District of Columbia and union-organizing legislation and in favor of gun owners' rights. Ensign has been a member of the men's ministry the Promise Keepers, a Christian ministry. He had been highly critical of former Sen. Larry Craig, R-Idaho, who served in Congress for a quarter- century when he was arrested in an airport bathroom. Ensign stopped short of urging him 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. Ensign is the latest member of Congress who has acknowledged infidelity. Sen. David Vitter, R-La., is rebounding from being linked with a prostitute by appealing to the populism in his state. Over the years, Ensign and Senate Majority Leader Harry Reid, D-Nev., have worked closely on issues affecting Nevada and have an agreement not to criticize the other publicly "Sen. Reid's thoughts are with Sen. Ensign and his family at this time." Reid spokesman Jon Summers. Republicans lost eight seats last November under Ensign's campaign leadership, with one race, in Minnesota, still undecided. The losses put Democrats within one seat of having a 60-40 majority, enough to prevent the GOP from blocking bills and appointments if all of them vote together.