States with most potential for Kerry upside/Bush downside

In adition to an estimate of the probability of winning the election, it's also instructive to see how sensitive this probability is to changes in state poll results. That is, which states impact the result the most if their polls change in favor of one candidate or another?

In the figure on the left, we see the resulting probability of an Kerry win, given changes in state polls from the five states with the most potential upside for Kerry or downside for Bush.

To keep the figure easy to read, it only includes the resulting probability of an Kerry win. The resulting probability of a Bush win was simply 100 minus the probability of an Kerry win.

As of November 2nd 2004, just before the election, Florida, California, Michigan, New Jersey, and Georgia had the most potential upside for Kerry. If any of the state votes changed by 10% in favor of Kerry (i.e. 5% switched from Bush to Kerry in any state), Kerry's probability of winning would have increased to 26%-28% and Bush's probability of winning would have dropped to 72%-74%

States with most potential for Kerry downside/Bush upside

This figure is similar to the previous one, with the only difference being that it corresponds to changes in state votes from the five states with the most potential downside for Kerry or upside for Bush.

Again, to keep the figure easy to read, it only includes the resulting probability of an Kerry win. The resulting probability of a Bush win is simply 100 minus the probability of an Kerry win.

As of November 2nd 2004, just before the election, New York, Ohio, California, North Carolina, and Illinois had the most potential downside for Kerry. If any of the state votes changed by 10% in favor of Bush (i.e. 5% switched from Kerry to Bush in any state), Kerry's probability of winning would have decreased to 13%-16% and Bush's probability of winning would have jumped to 84%-87%

Probability of achieving different electoral vote results

In addition to looking at probabilities of Kerry or Bush winning, we can also look at the probabilities of achieving different electoral vote results. That is, what is the probability that Kerry or Bush would have collected say, 270, 285, or 300 electoral votes? (Note that the probability of either of them winning the election was the probability that they would collect 270 or more electoral votes).

The figure on the left shows the probabilities of each of the candidates achieving given electoral vote totals, which vary from zero to 538. The points where the curves are the highest correspond to the most likely electoral votes for each candidate, as of November 2nd 2004, just before the election.