Reihan thinks Jim DeMint "comes closest to filling the Palin vacuum" if she doesn't run. Bernstein runs through candidates for the Republican nomination. He too wants to know more about DeMint's chances:

[I]t sure seems to me that Jim DeMint is the current leader of the hard-core conservative faction of the Republican Party.  He's far more consistent with his endorsements than any other conservative leader, and unlike Palin he can claim that he's actually been doing something effective for the cause.  For the conservative/Tea Party faction, presumably the trick is to be as far to the right as possible without actually sounding crazy to those outside the faction (and thus perhaps drawing vetoes from more pragmatic conservatives, and possibly some GOP-aligned interest groups).  At least as I read the reporting, DeMint seems to be pretty good at keeping to that line, and he certainly must be more reliable both for that crowd and for more pragmatic types than Palin.