As Republicans descend on Tampa, a TIME/CNN/ORC poll shows President Obama ahead of Mitt Romney 50 percent to 46 percent among likely voters in the Sunshine State.

Among registered voters, the gap is much larger -- 51 to 42 percent. A recent Quinnipiac/CBS/NYT poll found a slightly closer race, at 49 to 46 percent.

CNN also finds a dead heat in North Carolina, with Romney at 48 percent and Ryan at 47 percent among likely voters.