Sen. John Ensign announced Thursday he is resigning from his seat in Congress, where he served for 11 years, and he will send a letter to Vice President Joe Biden on Friday stating that his resignation from office will be effective on May 3, 2011.
Ensign, R-Nev., who is still a subject of a Senate Ethics Committee investigation, said in a statement that he has done nothing wrong and will not subject his family to more public scrutiny.
"While I stand behind my firm belief that I have not violated any law, rule or standard of conduct of the Senate, and I have fought to prove this publicly," he wrote in his prepared statement, "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. For my family and me, this continued personal cost is simply too great."
Ensign, 52, announced earlier this year he would not seek reelection to a third term in 2012.
In 2009, the senator admitted to an extramarital affair with the wife of his former top aide, Doug Hampton, which was soon followed by the revelations that Ensign's parents paid the Hamptons $96,000, and that the senator helped Doug Hampton find a lobbying job.
Last December, the Department of Justice dropped its investigation related to payments he made to his former staffer.
"I am gratified that, after extended investigations, both the Department of Justice and the Federal Election Commission saw no grounds on which to charge me with improper conduct," said Ensign in Thursday's statement. "I was hopeful that, with the closure of these investigations against me, the wear and tear on my family and me would soon be over. This was not the case."
Ensign said the Senate Ethics Committee recently decided to devote more resources to its investigation by hiring an outside counsel.
There are two House members actively running for the Ensign's Senate seat -- Shelley Berkley, a Democrat, and Dean Heller, a Republican.
Republican Gov. Brian Sandoval, who already has endorsed Heller, will appoint a successor, according to The Associated Press.