Republican Sen. John Ensign of Nevada will turn in his official resignation letter on Friday amid allegations of misconduct.
The Silver State's junior senator has been the subject of an ethics probe, investigating whether he had an affair two years ago with a former staffer and then helped that woman's husband get a lobbying job. Ensign has insisted he's done nothing wrong.
The Senate Ethics Committee named a special counsel in February to look into the matter. This came after the Justice Department and the Federal Election Commission investigated and then dropped their cases.
Ensign insisted Thursday that he's done nothing wrong and said the appointment shook him because he had hoped the probes would end with the Justice Department.
"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," he said.
"As is its right, the Senate Ethics Committee is continuing its investigation of issues into which it has been inquiring for the past year and a half. Indeed, the Committee even decided recently to devote more resources to its investigation by hiring an outside counsel even though the issues have been viewed and reviewed by so many others," he said.
In his statement , Ensign said that he could no longer put up with the intense focus of the affair and the ethical issues.
"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," he said.
Ensign announced in March he would not pursue re-election in 2012 to protect his family from campaign attacks.
Ensign's resignation would be effective May 3. According to Nevada law, Republican Gov. Brian Sandoval would appoint someone to serve the remainder of the term, which expires at the end of 2012.