Democrats:
2-1 Hillary Clinton
5-1 John Edwards
8-1 Random Democratic senator
9-1 Barack Obama (or whatever his name is)
Republicans:
3-1 Jeb Bush
5-1 Random Republican governor
6-1 Rudy Giuliani
9-1 John McCain
Independents:
1-1 Ralph Nader
666-1 Cthulhu (of course, if he actually decides to run, all bets are off)
Libertarians:
2-1 Someone of whom you’ve never heard.
5-1 Penn Jillette