Most political prognosticators delay their final predictions for a presidential race until the morning of Election Day. In 2016, for example, Nate Silver of FiveThirtyEight and Nate Cohn of the New York Times released their final projections during the wee hours of November 8. One forecaster, however, routinely publishes his predictions six months in advance. Professor Helmut Norpoth of Stony Brook University in New York issued his last word on the Trump–Clinton contest 246 days before the voters went to the polls. In March 2016, Norpoth confidently predicted that Donald Trump would be elected president. He not only contradicted Silver,...