But it's not quite that dependent either. There are stages of dependencies. Some states hang together more tightly (Northeast, West Coast, and Deep South) than others (Midwest and Southeast). And gradual shifts can be detected through polling and pinned to real world events (conventions, crises, etc). The campaigns use game theory to move resources accordingly (see McCain now in Minnesota versus pulling out of Michigan). Obama has a very strong firewall.

That's where, I guess, 538.com has taught me so much. The polls are a constant flow of changing opinions. But if your models are sensitive and well-designed you can see the slow wave shifts developing. It's not predictive, but history helps too. For instance, no candidate has ever been this far up, with this little time left, and lost.