Lots of people are following Nate Silver’s election tracking over at 538, especially his top-line estimate of the probability that Barack Obama will be re-elected in November. Silver has that number at 79.7% today. Sounds like good news for Obama. But it’s hard to get a gut feeling for what that number means. Yeah, it means Obama has a 4 in 5 chance of winning — but since the election isn’t going to happen 5 times, that proportion doesn’t quite engage the intuition.
Here’s one trick I thought of, which ought to work for baseball fans. The Win Probability Inquirer over at Hardball Times will estimate the probability of a baseball team winning a game under any specified set of conditions. Visiting team down by 4 in the 2nd, but has runners on 2nd and 3rd with nobody out? They’ve got a 26% chance of winning. Next batter strikes out? Their chances go down to 22%.
So when do you have a 79.7% of winning? If we consider the Obama-Romney race to have started in April or May, when Romney wrapped up the nomination, we’re about 2/3 of the way through — so let’s the 7th inning. If the visiting team is ahead by 2 runs going into the 7th, they’ve got an 82% chance of winning. That’s pretty close. If you feel the need to tweak the knobs, say the first two batters of the inning fail to reach; with two outs in the top of the 7th, bases empty and a 2-run lead, the visitors win 79.26% of the time, just a half-percent off from Silver’s estimate.
So: Obama 5, Romney 3, top of the 7th. How certain do you feel that Obama wins?
Update: (request from the comments) Silver currently has Obama with an 85.% chance of winning. That’s like: home team up 5-3, visitors batting in the top of the 8th, runner on first with one out.