Ethically hobbled Sen. John Ensign (R-Nev.) will submit his resignation to Vice President Biden, who, as president of the Senate, must be in receipt of such missives.

“It is with tremendous sadness that I officially hand over the Senate seat that I have held for eleven years,” Ensign writes. “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.” The turbulence is otherwise known as the numerous investigations — ethics and otherwise — into Ensign’s affair with a staffer who was the wife of another staffer and the payments from his parents to the mistress and her family. Said payments were made “out of concern for the well-being of longtime family friends during a difficult time,” according to the parents’ lawyer.

Ensign’s resignation comes more than a month after he announced he wouldn’t seek reelection. The question now is what took him so long to come to the conclusion that he needed to skedaddle from the Senate, effective May 3? It couldn’t possibly be a crisis of conscience. While the Justice Department dropped its probe, the Senate ethics investigations continued. Perhaps the gumshoes found something. We may never know. Once the member of Congress resigns, the investigations stop.