In no particular order. With the odds.
Mitt Romney (3.5 to 1)
Most likely to be the nominee not because he's popular, he's not, but because Republicans traditionally choose the Next Person In Line (think Bob Dole and John McCain). He lacks the charisma of a damp dishrag, his signature act was the precursor of ObamaCare, and most evangelicals think he belongs to a cult (Mormonism). Still, he is next in line.
Newt Gingrich (15 to 1)
Not nearly as smart as he pretends. Can't think on his feet, or sitting down on Meet the Press for the 35th time. Rudy Giuliani says, "He comes up with, you know, two ideas every minute." Bet you can't think of two ideas Newt's come up with in the past decade.
Sarah Palin (13 to 1)
She's dumb, but not that dumb. Caribou Barbie is making a fortune doing something she can't fail at (talking incoherently). Run and lose and she will kiss all that free money goodbye.
Michelle Bachmann (15 to 1)
She is that dumb. She'll run as the Tea Party standard bearer and may end up as Romney's running mate.
Ron Paul (34 to 1)
Really believes that the only thing wrong with the Gilded Age is that Southern slave owners where not properly compensated for the property they lost with emancipation.
Herman Cain (not listed, figure 20 to 1)
The candidate for people who don't want to be seen supporting Ron Paul. A carbon copy of Paul, he holds exactly the same beliefs down to waxing nostalgic over the Jim Crow laws that oppressed his family.
Jon Huntsman (9 to 1)
Who? Too unknown and too liberal. His best hope is to be the Veep for a radical conservative like, say, Bachmann.
Gary Johnson (51 to 1)
Who? I mean it. Who???
Rick Santorum (34 to 1)
The perfect 14th century candidate. Thinks torture is useful and has spoken out in favor of the Crusades.
Tim Pawlenty (5 to 1)
The best campaigner of the bunch. His problem is nobody knows, or cares, what he thinks. He is also burdened by being the less interesting Minnesotan after Bachmann. If anyone can dethrone the Mittster it will be Timmy.
Mitch Daniels (7 to 1)
Pawlenty's doppelganger. You could stand them side-by-side with their political positions and nobody could tell one from the other.
John Bolton (not listed)
A one-trick pony (Bomb Iran!). Only campaigning in New Hampshire because they have the better B&Bs.