I think at this point, the GOP nomination is definitely George Allen's to lose.
The 'Rat nomination will be whoever seems the most likely to get the moderate vote, and I think Mark Warner probably ruined that by giving former felons in Virginia the right to vote. I think the most likely 'Rat nominee is either Bill Richardson, Joe Lieberman or Dick Gephardt.
According to this article, Warner will have several defenses, including that most other states automatically restore felons' voting rights after release from prison, that he had to clean up the backlog of applications left by the previous administration, and that George Allen restored the voting rights of 460 felons while governor of Virginia.
Gephardt is in the "finally raking in private sector cash after retirement from politics" phase of his career. I wonder if he really wants the job, or could afford the pay cut.
Lieberman is too far right for today's Democratic party, he looks old, and he has the charisma of a lawn chair.
I guess Richardson is a contender, at least on paper. Somehow he doesn't seem presidential.