Herman Cain is on a roll. His support has tripled in just three weeks, landing the former pizza exec with 18 percent support, only 2 points away from Mitt Romney, according to a new Gallup survey. Rick Perry, on the other hand, is supported by only 15 percent of Republicans and right-leaning independents. That number is half what it was a month ago. Gallup predicts the nomination will be narrowed down to a three-way grab between Romney, Perry, and Cain—whose performance in recent debates seems to be behind his current surge.