In his new book, Jonathan Karl captures Donald Trump gloating. “She said she could never get crowds like that,” the former US president turned de facto Republican presidential nominee is quoted as saying, after a conversation with Angela Merkel, then chancellor of Germany. “In fact, she told me that there was only one other political leader who ever got crowds as big as mine.” One Republican congressman, Karl notes, was left wondering whether Trump understood that Merkel was alluding to Adolf Hitler. Asking: “Which would be more unsettling: that he didn’t or that he did?”, Karl leaves the reader to...