For Donald Trump, the latest recurring question around his candidacy—incited by the liberal left and parroted by even some Republicans—is whether he has the right temperament to be Commander in Chief. With Trump, what you see is what you get. Through the course of the campaign, that’s been one of his greatest attributes and it explains why so many Americans, tired of politics as usual, are rallying behind him. What is so hard for Trump’s detractors to grasp is that what they don’t like about Donald Trump has nothing to do with temperament—he’s got it. He’s proved over the course...