Newt Gingrich and Mitt Romney visited South Florida today to court the state’s potent Hispanic vote, as new polls showed the former House speaker overtaking his rival for the Republican presidential nomination. Voter demographics highlighted the reason the candidates are targeting Miami-Dade County: It has 368,000 registered Republicans, of whom 72 percent are Hispanic. All told, Florida has 1.5 million Hispanic voters, amounting to 13.4 percent of the electorate. Of that group, Cuban-Americans are the largest bloc, 32 percent.