The highly anticipated debate in Denver was the rarest of all things in American politics: an unspinnable event. Almost all who watched the contest concluded that there was one president on the stage, and it was Mitt Romney. Obama sympathizers took the measure of the situation and decided that the best thing to do was to hoist the white flag and get out of Dodge. Chris Matthews asked, “Where was Obama tonight?” James Carville observed that it “looked like .  .  . President Obama didn’t want to be there.” A few half-hearted attempts to deflect the result by arguing that Mitt Romney...