The Nevada Republican, a leading conservative voice in his party who has been listed as possible presidential material, indicated that he plans to remain in office and that his wife of 21 years, Darlene, is standing by him.

The woman and her husband "were both close friends, and they both worked for me," Ensign said.

Ensign had the affair, from December 2007 to August 2008, with a woman who worked for his Senate campaign and his political action committee. The woman's husband, meanwhile, worked in Ensign's Senate office, according to an aide who spoke on condition of anonymity.

By May 2008, both were no longer employed by Ensign, the aide said.

Ensign did not name the woman. Sources with knowledge of the matter confirmed that the couple in question are Cindy and Doug Hampton of Las Vegas. Senate and Federal Election Committee records show that they fit the description outlined by Ensign and his aides.

Calls made to the pair were not returned late Tuesday. They did not answer the door at their Summerlin home.

Ensign did not explain why he chose to come forward with his admission of infidelity Tuesday.

A Washington source said Ensign decided to announce the affair after he was approached by the husband of the woman involved. The man asked Ensign for a "substantial" amount of money with the implication it would buy the couple's continued silence, according to the source.

It was not immediately known how much money might have been involved, or whether Ensign reported the incident to authorities. Neither Ensign nor his spokesman would comment on the matter.

ALL APOLOGIES

Wearing a grim expression, standing alone at an unadorned podium, Ensign spoke for just over two minutes at Tuesday's news conference at the Lloyd George U.S. Courthouse in downtown Las Vegas, where his local Senate office is housed.

He had flown home from Washington, D.C., earlier in the day to make the announcement, as word began to trickle out about the affair, missing a vote on a bill important to the travel industry.

"I came back home to Nevada to come forward and explain to the citizens of our state something that I was involved in about a year ago," said Ensign, tieless and wearing a blue dress shirt. "Last year I had an affair. I violated the vows of my marriage."

Ensign said he takes full responsibility for his actions and apologized to those he had hurt and disappointed: "my wife, Darlene, my children, my family, my friends, my staff and all of those who believed in me."

He and his wife went to counseling last year, he said, and have "rebuilt our marriage to where now it is even stronger than ever."

The senator offered a partial explanation of how the affair happened: Two couples, all very close friends, with one there to lend an ear when the other was having a tough time at home.

John and Darlene Ensign were separated from April to July 2008, the senator's spokesman, Tory Mazzola, confirmed Tuesday evening.

That would indicate the affair began five months before the couple separated and ended a month after they got back together.

"Our families were very close," Ensign said. "That closeness put me into situations during a very difficult time in my marriage which led to my inappropriate behavior. We've caused deep pain to both families, and for that I am truly sorry."

After reading his statement, Ensign said, "I will not be taking any questions," and exited through a side door.

Darlene Ensign, who did not attend the news conference, also put out a statement Tuesday, which was released by Ensign's staff.

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

Married in November 1987, the Ensigns have three children.

RISING STAR

Elected to the House of Representatives in 1994 and the Senate in 2000, Ensign worked his way up through his party's ranks to the No. 4 spot for Senate Republicans, chairman of the Republican Policy Committee.

From 2006 to 2008, he chaired the National Republican Senatorial Committee, the GOP's Senate campaign arm.

The current post in charge of the party's positions on legislative issues has made Ensign a highly visible spokesman for the opposition party's point of view, appearing frequently on cable news shows and in the national political press.

Earlier this month, Ensign sparked speculation he might be jockeying for national office by traveling to Iowa -- something no politician does accidentally, according to an old political adage -- to speak to a conservative group, the American Future Fund.

For now, those aspirations will be stalled by the affair, according to an expert, but Ensign might well be forgiven by his constituents.

It's likely that Ensign will lower his profile for a while: no more speaking engagements or spots on national cable, said University of Nevada, Reno, political science professor Eric Herzik.

There were signs this week that Ensign was already preparing to lie low. A barbecue dinner fundraiser he was scheduled to headline in Nevada on Friday was postponed, according to the host group, the Republican Renewal Project.

"He had a nice trajectory for more national prominence, and that has been, at best, stalled, because he is now going to have to deal with this issue both personally and politically," Herzik said.

But damage to his standing within Nevada, where polls show him among the more popular elected officials, should be minimal, Herzik said.

"I don't know that an affair is a career-stopper if you handle it the right way," Herzik said. "Ensign got out in front and released the news himself. By the time he runs for re-election (in 2012), it will be old news."

A former veterinarian whose campaign ads have shown him cuddling puppies, Ensign was elected to the Senate in 2000 after narrowly losing a bid to defeat Sen. Harry Reid, D-Nev., in 1998.

Despite that tough race, Reid and Ensign became close friends after the 1998 election. On Tuesday, Reid said through a spokesman that his "thoughts are with Sen. Ensign and his family as they go through this difficult time."

PAST WHISPERS

Whispers of impropriety have dogged Ensign before. In February 2002, he took a sudden two-week leave from the Senate that was never explained.

It was understood among his staff that the leave for "personal reasons" was a rescue mission of sorts for Ensign's troubled marriage.

At the same time, Ensign campaigned as a social and religious conservative who defended family values. A member of the Promise Keepers, he delivered the opening prayer at the Christian men's group's meeting in Las Vegas in 2003.

In 1998, Ensign was the first member of Nevada's congressional delegation to call for President Bill Clinton's resignation over his affair with Monica Lewinsky.

Speaking on the Senate floor in 2004, Ensign called for a constitutional amendment banning gay marriage, saying, "Marriage is the cornerstone on which our society was founded."

In 2007, Ensign was among the most prominent Republicans calling on Idaho Sen. Larry Craig to resign, calling Craig a "disgrace" for his arrest in an airport men's restroom on disorderly conduct charges.

On Tuesday, Ensign indicated he would not step down, saying, "I am committed to my service in the United States Senate and my work on behalf of the people of Nevada."

FAMILY FRIENDS

Doug Hampton and John Ensign were old, close friends when Ensign gave Hampton a top staff position in 2006, according to a former Ensign staffer.

"It was as if Ensign had put his brother on staff," the staffer said. "He (Hampton) had a lot of sway with the senator."

Hampton previously had worked for Sierra Pacific Resources, now NV Energy, in the utility's energy efficiency department, according to the company.

Hampton's position in Ensign's Washington office was "administrative assistant," according to Senate records. The former staffer described the post as a sort of "co-chief of staff."

Hampton worked for Ensign in the Senate from November 2006 to May 2008, records show, earning about $245,000 over that time span.

Meanwhile, according to campaign disclosures on file with the Federal Election Commission, Cindy Hampton was a bookkeeper for Ensign's political operations, including Ensign for Senate and Ensign's Battle Born Political Action Committee.

LEFT ENSIGN'S EMPLOY

In May 2008, the two abruptly left Ensign's employ and Washington, returning to Las Vegas and the Summerlin home not far from where the Ensigns live.

According to county records, the Hamptons purchased the five-bedroom, 4,360-square-foot property in 2004 for $1.23 million.

Zillow.com, a Web site than analyzes real estate information, now prices their home in Summerlin's Trails Village at $862,000.

Since leaving, sources said, Doug Hampton has worked as a consultant for Allegiant Air and for November Inc., the political consulting firm that runs Ensign's campaigns.

On Tuesday, signs of life could be seen through the front door window of the well-kept home, but no one answered the door.

A freshly washed Dodge Ram truck was parked in the driveway.

Review-Journal writers Mike Blasky and Brian Haynes contributed to this report. Contact reporter Molly Ball at mball@reviewjournal.com or 702-387-2919.