While Mitt Romney stays at the top of the pack, a series of Republican presidential contenders has risen and fallen as polls show that likely voters are politically fickle. The latest to move up is Newt Gingrich, with a possible backlash as what political pros call his "negatives" rise to the surface. A poll by Bloomberg News in Iowa shows Herman Cain and Ron Paul leading Romney, with Gingrich coming on strong. The range of support goes from 17 percent for him to 20 percent for Cain. Rich Galen, who was communications strategist for then-House Speaker Gingrich, is still a GOP strategist, and blogs at Mullings.com.