Modern American conservatism is composed of three distinct traditions: libertarian economics, foreign-policy hawkism and social traditionalism. This “fusion” was born of a contingent historical moment, the Cold War, when the Soviet threat forced different social classes and their ideological spokesmen to band together in common cause. There was no eternal principle demanding that these groups tie their destinies together — a fact that became apparent with Donald Trump’s rise, which divided the three camps along various axes of alliance and enmity.