U.S. Sen. John Ensign, R-Nevada - facing the possibility of public hearings and legal proceedings stemming from an affair made public in 2009 and ramifications leading to alleged conflict-of-interest violations by a former aide - said late Thursday he would resign, effective May 3.

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, he said in a statement.

While two government investigations by the Justice Department and Federal Electoral Commission have found no violations, he still faced an ethics investigation by a Senate panel. He may have also been subjected to further questioning after a former aide he dealt with - who took a job as a lobbyist - was indicted in March of conflict of interest charges. The former aide is the husband of the woman with whom he had an affair.

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.   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 - who has been a Senator for 11 years - said in March that he would not stand for re-election in 2012, citing expected campaign scrutiny of the affair with former campaign treasurer Cynthia Hampton he admitted to in 2009.

Ensign dismissed both Hampton and her husband Doug Hampton - an administrative assistant - in 2008 after the affair became known to the other spouses.

After the dismissal, Ensign's parents' gave a $96,000 gift payment to the Hampton family. Doug Hampton has alleged Ensign helped him line up lobbying clients and meetings with Obama administration officials after leaving official work with Ensign's office.

In February, a pair of Senators belonging to the Senate Ethics Committee investigating alleged violations said they were hiring a lawyer to determine if violations had occurred. Additional steps could have included a public hearing ahead of any disciplinary action, if warranted.

The U.S. Justice Department probed but handed down no charges against Ensign. Hampton, however, was indicted on March 24 of violating conflict-of-interest laws. He allegedly engaged in unlawful communication with Ensign's office, violating the Senate's revolving door policy.

Ensign said that beyond his Senate career he would continue to fight for a better country and for a future that our children deserve.