The former Godfather's Pizza executive, in his double-breasted suits and gold-colored ties, has wowed debate audiences with his preacherly cadence, his humor and his pizza slogan-worthy 9-9-9 approach to tax policy. (That would be a 9 percent income tax, 9 percent corporate tax and a new 9 percent national sales tax.)

Cain has also impressed his rivals, many of whom named him as a potential running mate in the last Republican debate.

Yet on that Florida debate stage, the choice of Cain as a hypothetical vice president was not so much a sign of his strength, but more of a feeling that Cain wasn't a true threat.

That may have changed somewhat after the debate. Cain scored an upset against Texas Gov. Rick Perry two days later, notching a double-digit win in the Florida straw poll. And in the most recent Fox News poll, Cain is in third place with 17 percent of the vote, statistically tied with Perry, in his strongest poll showing so far.