(Ron Sachs/picture-alliance/dpa/AP Images) Warren during a hearing in the Senate Committee on Banking, Housing, and Urban Affairs on January 23, 2018. F rom the moment he began running for president in 2015, it was apparent that Donald Trump was a kind of political idiot savant, even if the idiot part blinded so many people to the savant part. He seemed to know nothing about anything, yet he had an intuitive sense of what would get certain voters angry and excited. And he was nearly alone in believing there was almost nothing he couldn't get away with; his off-the-cuff assertion that "I could stand in the middle of Fifth Avenue and shoot somebody, and I wouldn't lose any voters, OK? It's like incredible" will stand as one of the most profound insights of the entire Trump era. Trump could also take the preferred tactic of the fourth-grade bully—mocking nicknames for those he seeks to dominate—and turn it into a potent political weapon. Liddle Marco, Lyin' Ted, Crooked Hillary—in every...