Frum thinks that Donald Trump is a bad man and a worse president and that his presidency endangers the American republic. Those opinions aren’t particularly original or particularly rare, but this book distinguishes itself by its literary quality and its intellectual breadth. Most anti-Trump literature acknowledges the economic concerns of Trump’s supporters and suggests that establishment politicians need to address them. Frum goes significantly further. He shows awareness of, and even sympathy for, their cultural grievances and their sense of dislocation. The book would be even better, and perhaps less alarmist, if Frum had looked more closely at the history of populism in the United States. Although quack economics and racism frequently accompany populist uprisings, populism has sometimes served as a useful corrective to out-of-touch elites. The Trump phenomenon should drive political observers on both sides of the aisle to deepen their understanding of populism, not to pander or surrender to it but to think intelligently about how to channel populist energy toward constructive reform.