As I write these words, American pundits and political junkies are struggling to come to terms with some curious, even alarming, developments. Donald Trump has claimed the Republican presidential nomination while advocating a ban on Muslim immigration to the United States and the construction of a wall along the Mexican border. While many would blame his rise on the particular dysfunction of the G.O.P. or of America’s political culture more generally, a larger context makes that view impossible. A populist and sometimes xenophobic campaign succeeded in persuading British voters to leave the European Union. Marion Maréchal-Le Pen has risen as a charismatic new star of the French right; Germany buzzes with the possibility of a backlash against Angela Merkel’s openness to Middle Eastern refugees. In May, Austria’s Norbert Hofer came within a percentage point of becoming the first far-right leader since World War II to win a national election in Europe. Far-right parties in the Netherlands, Poland, and even the traditionally liberal Northern European countries are enjoying a similar renaissance. The terms “nativism,” “reactionary,” even “fascism” appear in political conversation with increasing regularity. Though few of these leaders profess deep religious commitments, their popularity seems driven in significant part by religious ressentiment — an awareness of the decline of Christian (or “Judeo-Christian”) civilization and a determination to arrest and, if possible, reverse that decline.