Why would Davis be in any danger next year? He won easily enough in 2006.
He won with the lowest percentage of his career since he defeated Leslie Byrne in 1994, and his opponent only had 1/10th of the cash he had. If Leslie Byrne or Gerry Connolly, the chairman of the Fairfax County Board of Supervisors, runs, they will be fully funded, and the Democratic Presidential nominee will more than likely carry the district in 2008 (Kerry lost it by less than one percent). All this in an environment that's not looking like it will be much, if any, better for the Republicans than 2006 was.
It will also be a blow to his image if his wife loses her State Senate seat this year, which is looking more and more likely. He's been campaigning for her constantly, and she's recently dropped $750,000 in last-minute TV ads -- this for a State Senate district that will probably have a turnout of under 50,000 voters.