Although it is early, the best candidate I see now is George Allen.
Huckaby is a joke. Anyone from the Natural State is a Natural Loser. After all, we have Bill and Hill to prove that.
I think you're right if President Bush has some coattails to ride in 2008. I say this because Allen does appear to be best suited to keep together the coalition that Bush has succeeded in building.
But if the President is a non-factor in 2008 (ie low popularity), I unfortunately think the candidate that will win is McCain (health-willing) or Hagel.
Long story short...imho it's essential to get the President's popularity back on track to keep this country going in the right direction for the next 12 years.