The networks, as well as the rest of the media, will have some decisions to make tonight if, as I have long predicted, this is a lopsided victory for Obama.
Consider this. Virginia and most of Florida close at 7:00 -- and a huge number of Florida's votes are in early anyway; if Obama wins both by 5 points or more, the networks will be able to call them pretty quickly. Ohio and North Carolina close at 7:30, and the same applies for them. A bunch of states where the margin should be even greater -- including most of New England, Illinois, Michigan, Pennsylvania, and New Jersey -- close at 8:00 and could probably be called right away.
Which is to say, if things are going well for Obama, by shortly after 8:00 tonight the networks may very well have called 16 states worth 195 electoral votes, of the 270 needed. Which means it's all over, because there are another 86 EVs in the bag: in Califiornia, where polls are open until 11:00 ET, and New York, where polls close at 9:00.
The media likes to not declare a victor while polls are still open in the lower 48 states. But can they really play goofy for two to three hours?
In fact, the facade could be gone well before prime time even starts on the east coast. Indiana and Georgia close at 7:00, and Ohio, North Carolina, and West Virginia close at 7:30 -- any one of them getting called quickly for Obama, and certainly any two, means that there's no use pretending McCain can win.
My guess is that -- IF Obama in fact wins big -- the networks will acknowledge it and switch fairly early into heavy "how big/how historic" mode. It will be interesting to see which ones do it earlier rather than later/