By Nate Silver, New York Times Sunday Magazine, online September 18, in print September 23, 2012

[....] Obama and Romney can hope for good jobs numbers or terrible ones, and for calm in the Middle East or an eruption that hurts the administration. But one thing they can definitely control is how to allocate their resources­ for the best chance at 270 electoral votes.

Using my FiveThirtyEight model, I’ve determined — through about 25,000 simulations that I run each day — which states could put either candidate over the top. Crucially, the model takes into account not only how states poll relative to national trends but also to one another. Demographically similar states can rise and fall together. If Romney makes gains in Wisconsin, for example, he will probably also do so in neighboring Minnesota.

Perhaps more important, the program evaluates the order in which the states might line up [....]