Sen. John Ensign announced Thursday he's resigning May 3 after almost two years of investigations into his affair with his staffer's wife and his attempts to hide it. Though federal prosecutors have dropped their probe into the senator, Ensign was still facing a Senate Ethics Committee investigation into how helped the aide, Doug Hampton, get a lobbying job after Hampton found out his boss was sleeping with his wife, Cynthia. The resignation is embarrassing for Republicans, but good news for them in the long run because it means Nevada's governor will be able to appoint a Republican replacement, which will give the candidate a boost in the election. This will make Nevada "a battleground state on steroids," National Journal's Josh Kraushaar argues.

The ethics committee hired outside counsel earlier this year; before formal charges could have been filed, Ensign would have to give a sworn deposition, but it's not clear whether that's happened, The New York Times' Eric Lipton reports. Ensign was "hopeful" the investigation would end after federal prosecutors dropped their probe, The Hill's Shane D'Aprile and Emily Goodin report. Hampton, however, was less fortunate, and pled not guilty earlier this month to charges that he violated revolving door rules by lobbying his former colleagues too soon after quitting his congressional work.

• Most bloggers on the right and the left continue to be creeped out by Ensign's behavior. Michelle Malkin writes, "Shame on Ensign for dragging his feet. Shame on the Beltway GOP leadership for not doing more to force Ensign out sooner." This puts "an end to the career of one of the sleaziest, most despicable GOP hypocrites to ever hold office, a man who built his political capital by preaching 'family values' and 'defending traditional marriage,'" Little Green Footballs' Charles Johnson says.
• But aside from the gross factor, many are considering what Ensign's quitting means in Washington. Gov. Brian Sandoval is expected to appoint Rep. Dean Heller, who already said he's running for Ensign's seat. Hot Air's Allahpundit notes, "The big loser here, notes Dan 'Baseball Crank' McLaughlin: Grassroots conservatives who might have been hoping to primary Heller. I think that was a small-ish risk given his sterling poll numbers and the fact that tea partiers seem more attuned to electability now (especially in Nevada!), but the point is well taken."
• Slate's Dave Weigel thinks Sharron Angle loses out, too. The Tea Partier who almost took down Sen. Harry Reid last fall is running for Heller's congressional seat. If Heller is appointed, there will be a special election for his seat, the candidates might be picked by party committee. Angle would do better with a snap election, he says.
• But The New York Times' Nate Silver argues that Republicans shouldn't celebrate too hard. Appointed candidates don't do as well electorally as incumbents--while 88 percent of incumbents are reelected, appointed senators win only half the time. Heller's real benefit might be that he "probably won’t have to take as many potentially risky votes as those in the House, where they are pushed more by the Tea Party caucus--although Mr. Heller has already voted for Paul Ryan’s budget, which Democrats will try to turn into a liability."

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Elspeth Reeve