Our understanding of antebellum anti-Catholicism by and large remains rooted in a scholarly consensus that emerged years ago. Equal parts ethno-religious bigotry and economic anxiety, the origins of this consensus can be traced back as far as Ray Billington’s 1938 work The Protestant Crusade. This essay argues that as much as this consensus explains, it misses an important strain of anti-Catholic discourse called here “ideological anti-Catholicism.” Responding to the failed revolutions of 1848, ideological anti-Catholics challenged the Church as a political actor not as a spiritual home. Exploring the contours of ideological anti-Catholicism helps us broaden our understanding of antebellum politics, intellectual life, and the boundaries between church and state.