With the last set of polls factored into the model, my final prediction is Obama to win 332 electoral votes, with 206 for Romney. This is both the median and the modal outcome in my electoral vote simulation, and corresponds to Obama winning all of his 2008 states except Indiana and North Carolina.
The four closest states – and therefore the most difficult to predict – are Florida, North Carolina, Virginia, and Colorado. Of these, my model only expects Romney to win North Carolina; but Florida is a true toss-up, with just a 60% chance of Obama victory. I would not be surprised if Florida ended up going for Romney. If that happens, Obama would win 303 electoral votes, which is the second-most likely scenario in my simulation. The third-most likely scenario is that Obama wins 347 electoral votes, picking up North Carolina in addition to Florida.
It’s been interesting to watch the forecasts of other poll watchers converge on the 332 estimate. Sam Wang, at the Princeton Election Consortium, also sees 332 as the modal outcome. So does Simon Jackman at the Huffington Post, and Josh Putnam at FHQ. Nate Silver, at his FiveThirtyEight blog, reports the mean of his electoral vote simulation at 313 – effectively splitting the difference on Florida, which he currently rates a 50.3% chance of an Obama win. But his most likely outcome is still Obama 332, followed by 303 and 347, just like me. Update: both Wang and Jackman revised their forecasts slightly downward this afternoon, based on late-arriving polls.
There will be plenty of opportunities to evaluate all of these forecasts once the election results are known. I’ve already laid out the standards I’ll be using to check my own model. This is how quantitative election forecasting can make progress, and hopefully work even better next time.
I’ll add, though, that on the eve of the election, averaging the polls, or running them through any sort of sensible model, isn’t all that hard. We are all using the same data (more or less) and so it doesn’t surprise me that we’re all reaching similar conclusions. The real challenge is producing meaningful and accurate forecasts early in the campaign. My model is designed to be robust to short-term fluctuations in the polls, and converge in a stable and gradual manner to the final, Election Day estimates. It appears that in this regard, the model has worked as intended.
But from a broader perspective, my model has been predicting that Obama will win 332 electoral votes – give or take – since June. If all of us are correct today, the next question to ask is when each model arrived at the ultimate outcome. That’s a big if, though. Let’s start with how the votes come in tonight, and go from there.