Barbara McQuade’s book is a piercing exposé of how Trump is eroding democracy by turning the US into a mafia state “I believe in America.” So says Amerigo Bonasera, a humble funeral director, in the opening scene of the 1972 film The Godfather. As Barbara McQuade recounts at the start of her new book, Bonasera has come to the shadowy office of Vito Corleone to ask him to avenge a brutal attack on his daughter. Ultimately, Corleone agrees, whispering: “Someday, and that day may never come, I’l...