Let me explain.
Sandy is a hurricane. Hurricanes hit Florida and North Carolina relatively frequently. Hurricanes require swift, immediate, decisive federal government response. President Obama has made a superb, swift, and decisive response to Sandy, where in the past Republican leaders in the federal government (i.e. George W. Bush with Rita and the 2005 Florida hurricanes, as well as, obviously, Katrina) didn't do a good job with their response. And I think that voters in Florida and North Carolina recognize the differences between those opposing scenarios.
My thought is that some Florida and North Carolina voters will note the decisive action that President Obama has taken and is taking, as well as remember the non-action of George W. Bush, and choose the candidate of the party with a better record on disaster preparedness and relief. The candidate of "this is an essential government function" instead of the "send it back to the states" candidate.
Admittedly, it probably won't make that much of a difference. But in Florida, where the race is within margin of error, it might just be exactly what Barack Obama needed.