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Swing State Analysis

You should now an additional graph along the right-hand side of the page, which I have dubbed the ‘Swing State Analysis’. What this tells you is which states are likely to ‘swing’ the election. As I describe it here:

I’m now reporting another new parameter in my output, which is the state that “swings” the election in each of the simulation runs. The way that this works is as follows: I arrange the states from best to worst in order of Obama’s (or Clinton’s) vote share in each of the 5,000 simulations. I then count electoral votes upward until he equals or exceeds 269 EV. The state that puts him over the top is literally the swing state for that simulation run.

This is one of those things sounds fancier than it really is, and produces what should be fairly intuitive results. Obviously, the key variables in this calculation are the number of electors in a state, and just how tight the state is expected to be. These figures might be thought of as a good proxy for how the campaigns should allocate their resources, among other things.

What’s interesting is that we come up with relatively different lists in the Obama-McCain and Clinton-McCain scenarios. Pennsylvania, Ohio, and Michigan are important to both candidates to a lesser extent so is Missouri. But New Jersey and Virginia are featured prominently on Obama’s list, while they don’t make Clinton’s Top 15 (New Jersey because she won’t lose it; Virginia because she won’t win it). Florida, meanwhile, ranks much lower on Obama’s list than on Clinton’s, because the model thinks that he has a lot of alternative paths to 269 electoral votes that should provide a better return on his investment.

Nate Silver founded and was the editor in chief of FiveThirtyEight.