Washington (CNN) - In a potential setback for Democrats' hopes of maintaining majority control of the Senate, first term Virginia Democratic Sen. Jim Webb, a surprising winner in the swing state five years ago, announced Wednesday he won't seek re-election.
He is the third member of the Democratic caucus to announce he won't run in 2012. Democrats already faced the formidable task of defending 23 seats - many in purple states – compared to just ten, relatively safer, seats for Republicans.
Republicans need to pick up just four seats to gain control of the Senate.
"After much thought and consideration, I have decided to return to the private sector, where I have spent most of my professional life, and will not seek re-election in 2012," Webb said in a statement.
Webb, a former Secretary of the Navy in the Reagan administration, was elected narrowly in 2006 after the popular incumbent, Republican Sen. George Allen, stumbled in what is well known as Allen's "macaca moment." After several years in political exile, Allen announced recently he would run again for his old seat, potentially setting up a grueling rematch with Webb. Allen would first have to win the GOP nomination and is likely to face challenges from Tea Party candidates.
In 2008, President Obama was the first Democratic presidential candidate to win the state in decades but since then Virginia voters elected conservative Bob McDonnell as governor.
In a CNN interview with John King last month, Webb said he was weighing whether to run again.
"It's whether or not we want to make the decision to be up here for another 8 years and do what it takes to do that," he said.
"This was very much a personal thing for Jim Webb," a Democratic strategist involved in Senate campaigns told CNN. "The question was whether he and the stomach for the campaign and another six years on the job."
The strategist said the decision wasn't based on Webb's ability to win and that polling was not factored into the decision.
Webb, a centrist, was never a reliable vote for his Democratic leadership. He focused heavily on military and foreign affairs. Early in his term, he pushed through an updated GI Bill, a major accomplishment for a junior senator. Recently, he's taken up the cause of prisoner rights, an unlikely issue for a politician to champion since it's not high on the minds of most voters.