Evan Bayh: I do not love Congress. Watch video here

"To put it in words I think most people can understand: I love working for the people of Indiana, I love helping our citizens make the most of their lives, but I do not love Congress," Bayh said at a news conference Indianapolis, where he was joined by his wife and two sons.

"My decision should not be interpreted for more than it is, a very difficult, deeply personal one," he said. "I am an executive at heart. I value my independence. I am not motivated by strident partisanship or ideology."

Bayh, 54, said he believed he would have been re-elected this November, despite "the current challenging environment." He said it was time for him to "contribute to society in another way," either by creating jobs with a business, leading a college or university, or running a charity.

"After all these years, my passion for service to our fellow citizens is undiminished, but my desire to do so by serving in Congress has waned," Bayh said at the news conference.

The Democrats will have to scramble to find a replacement candidate for Bayh's seat. Friday is the filing deadline for the May primary, although the party would have until June 30 to select a replacement candidate. (See full story here)