Canaries in the Coalmine
Surprising results in certain Eastern states would suggest that results differ by 3 points or more from pre-election polls. Possible causes include biases such as unexpected turnout effects, unrepresentative models by pollsters, or missing cell phone users.
Early warnings for a larger-than-expected Obama win: North Carolina (closing time 7:30 pm, Romney +1%). An Obama win would foretell a larger-than-expected re-election margin.
Early warnings for a closer race or a Romney win: The number one state to watch tonight is New Hampshire. New Hampshire is a homogeneous and quickly-reporting state. Obama has a lead of 3% in polls. If he wins by less than 1% or falls behind, tonight may be a nail-biter. A virtually must-win for Romney is Ohio (closing time 7:30 pm, Obama +3%).