I have to confess that this is a major surprise.

Indiana Sen. Evan Bayh will not seek re-election this year, a decision that hands Republicans a prime pickup opportunity in the middle of the country.

“After all these years, my passion for service to my fellow citizens is undiminished, but my desire to do so by serving in Congress has waned,” Bayh will say.

The biggest reason this surprises is because of the ferocity with which Bayh operatives and the DNC have attacked the entry of Dan Coats into the Senate race. Coats’ residency in North Carolina and damaging work as a Washington lobbyist got major attention, suggestive that national Democrats were working hard to push him out of the race. And now, as that was gathering success, Bayh decides to retire.

Democrats sort of have a bench here, and Barack Obama barely took Indiana in 2008, but this turns what looked like a pickup into a very difficult seat to hold. Whether Republicans go with Dan Coats or former Rep. John Hostettler, they’re going to be favored. No Democrat was eyeing this race because nobody possibly believed that Bayh would leave.

Putting IN-Sen in play seriously raises the possibility of a Republican takeover of the Senate in November. It’s still a long shot, but definitely in the realm of the possible.

UPDATE: The ballot deadline to file in Indiana is THIS FRIDAY. Bayh really has screwed the Democrats here (what else is new?). Possible candidates include Reps. Baron Hill, Brad Ellsworth and Joe Donnelly.

UPDATE II: What a pathetic child this guy is. Here’s part of his speech:

“Two weeks ago, the Senate voted down a bipartisan commission to deal with one of the greatest threats facing our nation: our exploding deficits and debt. The measure would have passed, but seven members who had endorsed the idea instead voted ‘no’ for short-term political reasons,” he said. “Just last week, a major piece of legislation to create jobs — the public’s top priority — fell apart amid complaints from both the left and right. All of this and much more has led me to believe that there are better ways to serve my fellow citizens, my beloved state4 and our nation than continued service in Congress.”

Nobody likes my bold ideas to cut taxes for billionaires and force seniors onto cat food, so… buh-bayh.

…More in Bayh’s statement here.

UPDATE III: There’s some confusion over the timing of the filing deadline in Indiana. Most people were under the initial impression that Democrats had until Friday to field a candidate. Others are reporting that the deadline is actually tomorrow at noon. And, Ben Smith tweets that Indiana Dems could fill a primary vacancy anytime between now and June 30th. So it’s unclear what the reality is here.

UPDATE IV: It does look like the state Democratic Party would be able to choose a candidate to succeed Bayh. The only monkey in this wrench would come if Tamyra D’Ippolito managed to get all 4,500 signatures needed to qualify for the ballot. But I’d say that’s unlikely.

I wouldn’t rule out the IN Dems selecting… Evan Bayh, after national Democrats cajoled him back into running.

UPDATE V: Bayh apparently told his staff about this on Friday, and it didn’t leak. In fact, MSNBC is reporting that Harry Reid didn’t know until an hour ago when this all came out.