It takes loyalty to rise in Donald Trump’s world. And on Saturday, July 13, Karoline Leavitt demonstrated it in uncommon fashion. As she tells it, Trump’s then-campaign spokeswoman had only just carried her 3-day-old baby boy home from the hospital when she switched on the television to watch her boss’s campaign rally in Butler, Pa. It turned out to be the fateful event at which a would-be assassin’s bullet clipped Trump’s ear. Almost immediately, according to Leavitt, she and her husband decided: She would scrap a planned maternity leave and go back to work, which she did four days later....