David Austin Walsh examines the relationship between the American far right and mainstream conservatism from the 1930s through the end of the Cold War. Challenging narratives that treat extremism as a marginal phenomenon periodically expelled from a fundamentally moderate conservative movement, Walsh shows how far-right elements were foundational in creating the political culture that culminated in the Reagan era. He traces connections between 1930s pro-fascist movements, postwar anti-communism, and the institutions that built modern conservatism: think tanks, magazines, direct mail networks. Walsh, a historian at Yale, draws on extensive archival research to demonstrate that figures later dismissed as extremists played crucial roles in shaping conservative ideology and organization. The book examines specific individuals and institutions, showing how ideas and personnel moved between respectable conservatism and its further reaches. Walsh argues that the relationship was not simple infiltration but rather mutual constitution: mainstream conservatism absorbed and moderated far-right energies, but was also shaped by them. This historical analysis offers perspective on contemporary debates about the boundaries of acceptable conservatism.