Unlike the other men on your list, Mr. Romney ran vigorously against illegal immigration in the primary, including in Florida. Cuban immigrants may by definition be legal but people perceive it as an attack on them to impress people who are uncomfortable with Hispanic immigration.
Well, that is a nice theory, but one can examine recent polls on this forum of California, Nevada, and Florida, and note that Romney is gaining among Hispanics.
Or, one can examine that Rick Scott ran vigorously against illegal immigration, including endorsing the recent arizona law, in the 2010 elections and still got half of Hispanics.