The early front-runner in the 2012 GOP presidential race, Romney slipped behind Texas Gov. Rick Perry after he entered the race with a splash in August. Most major polls showed Perry in the lead from mid-August until mid-September.

But a series of missteps along the campaign trail — coinciding with the rise of Herman Cain, who has stripped away some votes from Perry — has given the top-dog status back to Romney.

Because Romney does better with independent and centrist voters who sway general elections than do most of his primary counterparts, many Democratic groups are already working aggressively to knock down Romney, in hopes that a less viable Republican will win the primary and shore up Obama's reelection chances.