Virginia’s political scene was rocked on Wednesday with the announcement by Senator Jim Webb that he does not intend to seek election to a second term of office in 2012.

Webb, whose maverick style has allied him at various times with comrades on both sides of the political divide, said he wants to return to the private sector when his first six-year Senate term is complete. He did not explain his decision in the emailed statement sent to the media on Wednesday.

A Marine combat veteran of Vietnam, he served as Secretary of the Navy under then-President Ronald Reagan, and he took a strong stand for veterans starting with his first day in elected office. His update of the GI Bill, for example, gives veterans a better deal from the government than they’ve had in decades. On the other hand, he frustrated conservatives by voting in favor of federalized health care, despite his stated reservations for the hurried process that brought the legislation before legislators.

Webb’s decision to leave the Senate puts his Democratic party in an uncomfortable situation. On the heels of a midterm electoral drubbing in which they lost control of the House of Representatives, Democrats in 2012 will be fighting to retain control of the Senate and reelect a president whose popularity has taken a beating during his first couple of years in office.

Of the 33 Democratic senatorial seats that will appear on the ballot around the nation, Democrats hold 23. Webb was hardly a shoo-in for reelection, but he surely would have had an easier time holding onto the seat than any new Democrat will have taking it in an open election. Webb, who was never more than moderately liberal, and whose opinions on guns and the military earned him points with some of Virginia’s more moderate conservatives, had a good chance to hold off his challengers in 2012 — including former Senator George Allen, who was looking for a rematch of the close race in which he lost his seat to Webb in 2006.

There has been plenty of speculation about potential Democratic candidates to stand up against Allen and whatever Tea Party or Libertarian candidate winds up in the mix — the solid money’s on former Gov. Tim Kaine — but nobody could draw votes from both ends of the political spectrum quite like Webb could. Kaine, in fact, is likely to be a polarizing figure because of his position as chairman of the Democratic National Committee and his close friendship with President Barack Obama.

Once solidly conservative at the federal level, Virginia has been going through some changes during the past decade or so, gradually moving from red state to blue as the left-leaning Northern Virginia area grows in population and political strength. The move toward blue became most pronounced when voters supported Obama for president in 2008. If Republicans are successful in taking back the Senate seat that Webb is vacating, that would give the state one Republican and one Democratic senator, once again leaving the state the perfect shade of purple.