Among Donald Trump's many shortcomings are the vast amount of history he doesn't know and the little he does. Perhaps someone told him that when Richard Nixon faced an unwelcome investigation, he fired the investigator. Perhaps no one told him it only made Nixon's plight worse. Trump owes most of his achievements to his talent for getting attention. Whether the attention was positive or negative was immaterial. His fame became larger and more lucrative either way. In the White House, though, making yourself conspicuous is not always a winning tactic. By firing the FBI director who was in charge of...