Win probabilities in elections

What's the probabiltity that Romney is leading in California?, from Ian Ayres at Freakonomics. Ayres makes the good point that even when a race is called a "statistical tie" or a "statistical dead heat", which seems to be a common term these days for polls where the two candidates are polling within the margin of error of each other, there's still information to be had. Just because a 2-point lead is within the margin of error doesn't mean that a candidate would freely trade being 2 points down for being 2 points up.