"Let me tell you what the Cain Doctrine would be: We ain't raising the debt ceiling," he said when he announced his presidential announcement. "We are going to cut the spending." Watch Cain's interview with ABC News' Top Line politics program.
The Candidate on the Fence - Michele Bachmann is the social conservative firebrand who has not entirely jumped into the race. She'll make that decision and announce it later this month in Iowa, where she would likely focus her campaign.
The Unheard -- Rick Santorum is struggling to be heard amongst all the other candidates. He officially announced his candidacy in Pennsylvania last week. But the former senator has had trouble gaining traction. He is an able debater, however, and will need a good performance. Watch Santorum announce his candidacy on "Good Morning America" with George Stephanopoulos.
The Godfather -- Ron Paul was not allowed in every debate four years ago, when he ran for president. The Libertarian-minded Republican's small-government idealism had a small but dedicated following then. It still does, although he seems prescient now and is in many ways the ideological godfather of the Tea Party. It is unlikely anyone will keep him out of debates this year. But with support in the single digits among Republicans, his road to the nomination will be a difficult one.
The No-Shows -- There are other possible candidates -- former Utah governor and Ambassador to China Jon Huntsman, who is considering a late entrance to the race, was in New Hampshire this weekend, but will not debate. Texas Gov. Rick Perry is said to be newly interested in a run, and may be able to poach the staffers who abandoned Gingrich. And there is Sarah Palin, who is taking a break after her bus tour of the Northeast. Palin's political ambitions are opaque and it is unclear whether she will run. She got 16 percent support in the USA Today poll out Sunday.
The Uninvited -- Former New Mexico Gov. Gary Johnson, who also has a libertarian bent, says he is running for president, but debate organizers decided he was not viable as a candidate.