National Journal's Charlie Cook, considered a top political analyst, has looked at the likely GOP candidates for president, and drawn interesting conclusions. Cook finds there is no Republican frontrunner; a situation that is quite unusual.
Furthermore, most of the plausible candidates are current or former governors. Although Cook doesn't mention it, the field suffers from a charisma deficit. The only two with pizzaz - Palin and Gingrich - also suffer from high negatives.
On the other hand, charisma should be less important in 2012 than it was in 2008, when Obama was a fresh, new face. Whatever else he may be in 2012, Obama will be neither fresh nor new. Reelecting him will achieve no civil rights milestones, electing him did.
A second term election is essentially a referendum on the president's first-term performance. Obama will have to run on his record; the GOP nominee will run against that record.