This article examines the Committee for Constitutional Government, a conservative organization that spearheaded a novel form of mass-based mobilization and direct-mail propaganda to counter New Deal reforms from 1937 to the late 1950s. I argue that the members of the committee offered a supple and variegated response to New Deal liberalism, one with deep roots in the American past. Organizationally, the committee differed from other conservative groups of the period in the vastly greater reach of its propaganda, the small-donor financial base of its operations, and its extensive cultivation of a grassroots movement committed to right-wing reform. The committee was a critical political actor from 1937 to 1955, systematically shaping legislation and countering the trend toward social democracy in America. The ultimate result of its campaigns was to retard the growth of the administrative state and help formulate a cogent conservative critique of reformist liberalism.