Retire from what, exactly, in 2008? His gubernatorial term ends in 2005, and I believe he is not allowed to run for reelection. Were he elected senator in '06 the term would last till 2012.
I was referring to John Warner, the senior senator, who could well retire in 2008 and thus allow Warner to make a clean run for the senate and in such a race he would probably win, against Allen in 2006 however it would be tougher that said it would still be a very competitive race.
My view is that Warner isn't ready, despite a very solid record as VA Governor but he needs more experience IMHO and so a Senate run would make sense, I don't think he's ready for a presidential run and should serve at least a term as a Senator.
As for Edwards he should give up the idea that he could win in 2008, after four years of doing squat, he should intend look to recasting himself and making a run for governor in 2008.