Former Massachusetts Gov. Mitt Romney greets supporters at his caucus night rally in Des Moines, Iowa, on Tuesday, Jan. 3, 2012. (AP Photo/Charles Dharapak)

Photo by: Charles Dharapak

Former Massachusetts Gov. Mitt Romney greets supporters at his caucus night rally in Des Moines, Iowa, on Tuesday, Jan. 3, 2012. (AP Photo/Charles Dharapak)