The Nate Silver truthers: Is the Times' polling guru biased?

Nate Silver rose to prominence as a political forecaster in the 2008 election, accurately predicting the electoral results of 49 out of 50 states. Since then, his blog on The New York Times has become a go-to destination for political insiders who want the lowdown on where the presidential election is heading. Silver's numerical model, developed long before the election began, is based on polls from a variety of sources, including those that lean left and right. The polls are averaged out and adjusted according to each firm's historical track record of corresponding with election results. When a new poll is released, it gets fed into Silver's computer program, which then spits out a prediction. That formula has led Silver to report that Obama has nearly a 75 percent chance of winning what is widely perceived to be a tight race, leading conservatives to speculate that Silver is skewing the numbers.

The Nate Silver truthers, as they've come to be known, just received some fresh ammunition for their conspiracy theories from a mainstream publication, as Dylan Byers at Politico claims that Silver could turn out to be a "one-term celebrity":

Prediction is the name of Silver's game, the basis for his celebrity. So should Mitt Romney win on Nov. 6, it's difficult to see how people can continue to put faith in the predictions of someone who has never given that candidate anything higher than a 41 percent chance of winning (way back on June 2) and — one week from the election — gives him a one-in-four chance, even as the polls have him almost neck-and-neck with the incumbent.

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Of course, Byers is conflating the law of probabilities with polls showing a neck-and-neck race. (Silver gives the edge to Obama largely because of the incumbent's strong position in various swing states.) As James Fallows at The Atlantic explains, there's a huge difference:

Although this will be obvious to anyone who has visited Silver's site or understands what he is doing, I should probably re-emphasize this point: Saying that Obama has a 70-30 probability of [a] win is entirely different from saying he has a 40 point (70 minus 30) lead in the polls. A 70 percent win-probability means that on a large volume of statistical-model runs of the election, the results show an Obama victory 70 percent of the time. But 30 percent of the time, they show a Romney win.

Indeed, many pundits and analysts, including Silver, were not happy with the Politico article.

Silver:

Ezra Klein at The Washington Post:

Adam Sewer at Mother Jones:

Josh Barro at Bloomberg: