Fantastic news. Between his affair with an ex-staffer and the endless ethics committee investigation into payments made to her and her husband (a special counsel was appointed just last month), the guy was a dead man walking. Against Ensign, this would have been a gimme pick-up for Democrats in a year when they’re expected to lose the Senate. Now it’ll be close and, like Reid’s race against Angle, war to the bitter end.

Ensign made the announcement today during a noon news conference at the Lloyd George Federal Courthouse in Las Vegas. He isn’t resigning his seat — simply not pursuing his re-election in 2012.

He said he came to the decision in the last week or so, adding that a Senate Ethics Committee investigation had “zero effect” on the decision not to seek re-election.

“I just came to the conclusion that I couldn’t put my family through this,” he said.

He’s the third Republican (Kyl and Hutchison are the others) and eighth senator overall to pack it in this year. Sharron Angle insisted after losing to Reid that she has “lots of options” for 2012, but if she couldn’t harpoon Dingy Harry while riding the big red wave of 2010, realistically there’s no way GOP primary voters will gamble on her again. In fact, according to a PPP poll taken in December, 68 percent of Republicans think they should have nominated someone else last year. This time the nominee’s likely to be Rep. Dean Heller, whose favorable rating in that same poll was 46/23 and who led probable Democratic nominee Shelley Berkley 51/38 in a hypothetical match-up. He led three other Democratic candidates head-to-head too; Ensign, by contrast, trailed all four. Today is a good day, my friends.

Any Nevadans want to chime in on Heller or other possible nominees? A quick check of Wikipedia reveals that he voted against TARP, so he’ll be off to a good start with tea partiers.