As far as potential candidates: Sarah Palin and Bobby Jindal are obviously the two that are being looked at most closely by the conservative wing of the Party. Either one would be great.
If someone even farther to the right stood a chance, we might look at Jim DeMint, Tom Coburn, or Rick Santorum. Probably a long shot, though, but you never know. I think that it would be good if one of them ran, however. It would keep Palin or Jindal from being the farthest candidate on the right wing, and then Palin or Jindal could perhaps be painted as a more moderate choice to help win votes in the middle. David Petraeus may be great, but I think that too little is known about him and his positions.