WASHINGTON -- U.S. Sen. John Ensign said Thursday evening that he is resigning, bringing an end to a once fast-tracked political career while further shaking up the electoral landscape in Nevada.
Ensign leaves office under the cloud of a persistent ethics investigation that stemmed from an extramarital affair he acknowledged almost two years ago. The probe will end once the Republican no longer is under the jurisdiction of the Senate.
"It is with tremendous sadness that I officially hand over the Senate seat that I have held for 11 years," Ensign said in a late-afternoon statement. He said he planned to send an official letter of resignation today to Vice President Joe Biden, who formally presides over the Senate.
Ensign said his resignation would become effective on May 3.
The sudden vacancy would be filled through an appointment by Gov. Brian Sandoval. Insiders immediately speculated the appointee would be Rep. Dean Heller, the Republican who already is running for the Senate in 2012 and who has already been endorsed by the governor.
Ensign, 53, took a big hit to his reputation and struggled to regain his footing with colleagues and constituents after he admitted in June 2009 that he had carried on an affair with Cindy Hampton, his wife's best friend and the wife of Doug Hampton, a close friend who Ensign had given a job as one of his top aides in Washington.
Growing from the personal scandal were allegations that Ensign arranged for his parents to pay hush money to the Hamptons once the affair was brought into the open and that he smoothed over Doug Hampton's departure from his staff by setting him up as a lobbyist with access to his office and violating federal lobbying law in the process.
Ensign has denied any legal or ethical wrongdoing. In December he avoided prosecution by the Department of Justice.
But the Senate Ethics Committee continued to investigate amid signs it was stepping up its probe. In February the committee hired special counsel Carol Elder Bruce to manage the case.
Nevada political columnist Jon Ralston reported Thursday night via Twitter that two unnamed sources told him the Ethics Committee voted this week to proceed in the case, which would have provided motivation for Ensign to step down.
Without confirming the information, committee Chairwoman Sen. Barbara Boxer, D-Calif., and Vice Chairman Sen. Johnny Isakson, R-Ga., said in a statement that "Senator Ensign has made the appropriate decision."
"The Senate Ethics Committee has worked diligently for 22 months on this matter and will complete its work in a timely fashion," the committee leaders said.
Beyond initial evidence-gathering, the Ethics Committee could have voted to move into a phase that could include public hearings into allegations of wrongdoing, possibly leading to votes to formally reprimand or recommend the Senate take harsher action up to expulsion from the body.
While insisting on his innocence, Ensign acknowledged in his statement that the investigations finally proved too weighty. In his statement, he opened the possibility that the Senate was planning to move forward on hearings into his conduct, a highly public and embarrassing -- and potentially humiliating -- turn.
"I will not continue to subject my family, my constituents, or the Senate to any further rounds of investigation, depositions, drawn out proceedings, or especially public hearings," Ensign said. "For my family and me, this continued personal cost is simply too great."
There also was speculation that top Republicans in the state had stepped up their appeals for Ensign to step down and give Heller a head start in the Senate after Doug Hampton's indictment last month on criminal charges stemming from his work as a lobbyist.
"The turbulence of these last few years is greatly surpassed by the incredible privilege that I feel to have been entrusted to serve the people of Nevada," Ensign said. "I can honestly say that being a United States Senator has been the honor of my life."
There was limited reaction from senators to the news. Sen. Harry Reid, D-Nev., traveling in China, said Ensign "was a strong advocate for Nevada, and worked for many years to improve our state. I know this is a difficult time for the family, and I wish them all well as they work through it."
Ensign's departure throws a new curve into Nevada's electoral landscape, where the political class was bracing for a lineup of competitive campaigns for federal office in 2012.
In a statement, Sandoval called Ensign "a true conservative and always a fighter for the Silver State." But he declined to comment on naming a replacement, according to Mary-Sarah Kinner, his press secretary.
Nonetheless, the jockeying commenced almost immediately, with speculation focused on Heller, a Sandoval ally already running to replace Ensign, who announced last month he would not seek a third term.
An appointment would give Heller a big leg up, making him an incumbent well in advance of the November 2012 election to a full six-year term.
"Governor Sandoval has the authority to appoint individuals to the U.S. Senate, and I will respect whatever decision that he makes," Heller said Thursday night.
Rep. Shelley Berkley, D-Nev., who declared her candidacy last week for the seat, had no immediate comment. She faces a primary challenge from Byron Georgiou, who has raised $1 million so far, about half his own money.
Under state law, if Sandoval appointed Heller as U.S. senator, then he would be required to have a special election within 180 days to elect a replacement for the 2nd Congressional District seat.
The law also says there will be no primary election before the special election to fill the House vacancy in a seat for the House of Representatives. It was not clear how Republican or Democratic candidates would be chosen.
Pam Dupre, the spokesperson for the secretary of state, said officials are researching this and other questions about how vacancies are filled.
Historian Guy Rocha said the last time a Nevada governor appointed a U.S. senator was Oct. 1, 1954. Gov. Charles Russell appointed fellow Republican Ernest Brown to replace Democrat Sen. Pat McCarran, who died two days earlier of a heart attack. Brown served a little more than a month before he was defeated by Democrat Alan Bible.
Rocha added that a special election has never been held in Nevada to fill a vacancy in the House of Representatives.
Heidi Smith, the GOP national committeewoman in Northern Nevada, said Ensign's resignation would give Republicans the advantage in keeping the Senate seat.
"If Dean Heller is appointed, it will help him tremendously," Smith said.
Setting aside the possibility that Heller might be appointed to the Senate, Democrats took Ensign's departure to reaffirm their intention to fight for his seat.
"Nevada will remain a top target for Senate Democrats," said Guy Cecil, executive director of the Democratic Senatorial Campaign Committee.
"There will be a very clear choice for Nevadans between an uncompromising extremist like Dean Heller ... and Shelley Berkley, a true fighter for Nevada's economy and middle class," Cecil said.
It was the end of the line for Ensign, a mediagenic and well-spoken conservative who was beginning to eye higher office when he announced his extramarital affair to avoid the risk of Doug Hampton announcing it for him. Ensign had traveled to Iowa, the presidential caucus state, just weeks earlier.
Ensign was elected to the U.S. Senate in 2000, and won re-election easily in 2006. He came to Washington as part of the famous Republican class of 1994 that grabbed control of the House under the leadership of Rep. Newt Gingrich, who became speaker.
Ensign gave up his House seat to run for the Senate against Reid in 1998. He lost by 428 votes, but the experience bonded the two Nevada politicians into a friendship.
Review-Journal reporters Laura Myers and Ed Vogel contributed to this report. Contact Stephens Washington Bureau Chief Steve Tetreault at stetreault@stephens media.com or 202-783-1760.