You've got Fred Thompson, Michelle Bachmann (whom Pelosi and Emanuel are going all-out right now to knock out of Congress), Jindal, and Duncan Hunter. Hunter has a name-recognition problem (MSM screening him out). Fred less so .... Michelle's well known in the party, but less so by far than Palin.
Jindal is new, and he's from India (well, his parents are) and Louisiana, where he was beaten once by Mary Landrieu and James Carville because Jindal wouldn't fight dirty when they fought dirty (and that's the only kind of fight they have in Louisiana).
Fred and Sarah have the presence, Fred the experience and can sell people on being the President when he speaks. Sarah probably needs to serve a term as Fred's veep.
Last time around Fred didn't seem to have the fire in his belly.