From the 2008 Senate Guru:
Virginia: John Warner just announced that he will retire at the end of his current term, rather than seek re-election in 2008. Expectations are the following: for the Democrats, popular former Governor Mark Warner, who left office with an approval rating exceeding 80%, will enter the Senate race; for the Republicans, we may see a bloody primary battle between Rep. Tom Davis and former Gov. Jim Gilmore. Should expectations play out as such, Virginia should be considered to lean toward a Democratic pick-up. Let the polling (and hoping the Mark Warner does enter the race) begin!
This leaves Democrats with a golden opportunity to turn Virginia blue. In January 2009, we could be looking at a Virginia Senatorial delegation of Senator Jim Webb and Senator Mark Warner -- both working very closley with Governor Tim Kaine. And, with a massive GOTV effort for Mark Warner's campaign (should he run) in Northern Virginia, the Democratic presidential nominee will likely have an excellent opportunity to win in the Old Dominion State.