There’s been probably too much attention paid to New York Times blogger Nate Silver over the last few weeks. Some of the criticism he has received (including some from this page differing with his conclusions if not necessarily always with his methodology) has been justified. But in fairness to Silver, he appears to be sticking to his guns about the accuracy of his forecast that continues to show President Obama as a heavy favorite to win re-election. While not intending to belabor the issue of his accuracy more than necessary, I think it’s worth returning to the subject one more time both in order to clarify my differences with his approach.
Silver explained his forecast again this morning as he surveyed the latest round of polls on the presidential race:
Mr. Obama is not a sure thing, by any means. It is a close race. His chances of holding onto his Electoral College lead and converting it into another term are equivalent to the chances of an N.F.L. team winning when it leads by a field goal with three minutes left to play in the fourth quarter. There are plenty of things that could go wrong, and sometimes they will.
But it turns out that an N.F.L. team that leads by a field goal with three minutes left to go winds up winning the game 79 percent of the time. Those were Mr. Obama’s chances in the FiveThirtyEight forecast as of Wednesday: 79 percent.
Not coincidentally, these are also about Mr. Obama’s chances of winning Ohio, according to the forecast.
That is a reasonable sounding point of view, especially when it is coupled with Silver’s disclaimers about the possibility that his forecast could be wrong and noting that a lot of tossup states that he believes Obama will win are still closely contested. But the problem here is that despite Silver’s confidence that what we are looking at is a three-point lead for the president, it may be nothing of the kind, either in Ohio or in the country as a whole. The probabilities he alludes to in sports–such as those that can give us precise statistical odds about what happens when an NFL team has a field goal lead with three minutes to play or a Major League baseball team has a two-run lead in the ninth inning–are entirely accurate and reliable because there’s no doubt in a game as to what the score is. In politics there is no such certainty, rendering Silver’s rational Sabrmetric approach to political polling mere guesswork.