Logically, at least, the argument is over. Mitt Romney proved in Florida yesterday he is the strongest Republican candidate to challenge President Obama by clobbering Newt Gingrich in a third swing state. First came Iowa, where Romney almost won and Gingrich placed a distant fourth. Then Romney trounced the field in New Hampshire. Newt did not break 10 percent in the Granite State. All three states are more consequential in the general election than redder-than-red South Carolina, the scene of Gingrich’s only victory, because they represent the real prize in the 2012 election: the political center.