We'll know by 3AM. In fact, we'll pretty much know where the election is swinging early on.
It's not going to be close. Obama will have won outright the states he needed to win in order to get to 270 (probably more), even states still tallying into the wee hours of the morning. The election will be called early. Mittens will stand no chance of winning even with the rest of those states still counting. The Popular Vote doesn't mean jack shit in the end.