Two-term Sen. John Ensign, R-Nev., has announced he is resigning from the Senate, effective May 3rd.

"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, 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 in a statement. "For my family and me, this continued personal cost is simply too great."

The Nevada Republican already announced in March that he would not seek re-election in 2012 at an emotional news conference in his home state with his wife at his side, saying "there are consequences to sin."

Ensign had an affair with the wife of his top staffer, Doug Hampton, who resigned shortly afterward.

GOP sources said a Senate Ethics Committee investigation into the matter and Hampton's subsequent employment, possibly at the behest of the senator, was drawing to a close. The early departure could keep any committee report from being made public.

The senator's resignation was first reported by veteran Nevada political reporter John Ralston.

Nevada Gov. Brian Sandoval, a Republican, would appoint Ensign's replacement, a move that could elevate the current GOP candidate to replace Ensign, Rep. Dean Heller.