Nate Silver has done for elections what Bill James did for baseball. In fact, he got his start following in Mr. James’s footsteps, by developing PECOTA, a sabermetric system. When Mr. Silver started his FiveThirtyEight blog before the 2008 election, his statistically rigorous methods of poll analysis were criticized. Then he nailed the November 2008 vote: he predicted 49 of 50 states in the Obama-McCain showdown—he missed Indiana, which Obama won by 1/10th of 1 percent—and every Senate race. The New York Times wisely picked up his blog in 2010, and Mr. Silver signed a book deal that same year. In last year’s election—as you must already know—Mr. Silver hit 50 for 50, and his highly readable The Signal and the Noise: Why So Many Predictions Fail—but Some Don’t became a best-seller. Even his critics had to line up and apologize: it was time to raise a ruckus over Mr. Silver, an outlier if ever we’ve seen one.