Nevada Senator John Ensign to Resign

Here's a pretty strong sign that the ethics investigation against Nevada Senator John Ensign is making progress: He announced today that he's resigning effective May 3, reports the Las Vegas Sun. Ensign had previously announced that he wouldn't seek re-election, but this dramatically speeds the Republican's departure. "While I stand behind my firm belief that I have not violated any law, rule, or standard of conduct of the Senate ... I will not continue to subject my family, my constituents, or the Senate to any further rounds of investigation," he said in a statement. "For my family and me, this continued personal cost is simply too great."

Ensign has been dogged by scandal after revealing that he had an affair with a staffer two years ago. Among other things, he's been accused of steering business toward her lobbyist husband in an apparent attempt to keep things quiet, and the Senate Ethics Committee is investigating. Nevada's GOP governor is expected to appoint a Republican replacement so the party has an incumbent in place for the 2012 election. Politico thinks it's probably Rep. Dean Heller. (More John Ensign stories.)