This thesis reassesses the significance of the prominent journalist and political thinker Walter Lippmann within the intellectual history of American democracy in the early twentieth century. It argues that he shaped this history more distinctively and more contingently than the existing scholarship allows. Contesting the elitist vision of technocratic government associated with him by scholars since the 1980s, the thesis contends that he became influential because his democratic theory provided his contemporaries with a demanding account of political culture. By combining the conceptual resources of liberal constitutionalism with social psychology, Lippmann developed a particular kind of democratic theory, which explained opinion formation through the political dynamics of existing cultural environments, and which animated a particular mode of political thought in the early twentieth century. This mode made him into one of the leading theorists of American democracy in the 1910s and especially the 1920s. It also exposed him to sustained criticism during the economic and international crises of the 1930s and 1940s. At stake in this mode were the possibilities and difficulties of explaining politics in a modern democracy through cultural concepts.