In the early months of Trump’s candidacy, the Republican Party’s most important figures, people such as Marco Rubio, Ted Cruz, and Lindsey Graham, were united—and loud—in their scorn and contempt. Even more, in their outrage: Trump was a menace and an affront to our democracy. Then, awkwardly, Trump won. Thank You for Your Servitude is Mark Leibovich’s unflinching account of the moral rout of a major American political party, tracking the...