Donald Trump’s presidential victory in 2016 had many causes, but a bargain he made with religious conservatives belongs at or near the top of the list. Their support was crucial, especially once the death of Justice Antonin Scalia meant whoever won the election would tip the Supreme Court in his party’s favor. And that is exactly how it played out. For a while, it seemed like a good deal. Christian leaders spoke of Trump in the most generous terms and frequently acted as ambassadors between him and their followers, many of whom were uneasy about his uncouth persona. And Trump, with much guidance from his advisers, prioritized protecting religious liberty, restoring faith in public life, and, most importantly, appointing judges to the Supreme Court whose originalist understanding of the Constitution coincided with the religious Right’s...