While early studies of populism, usually dated from the 1960s, were highly interdisciplinary, contemporary research in this field is dominated by political science and political theory. This current phase of research is narrowly focused on certain forms of political action and remarkably reluctant to pathologize the US case. Social theory plays at most a marginal role. Recent historicizations of this field have failed to recognize the significance of the prior ‘missing first phase’ of populism studies (1940–65) led by key sociological (...) figures among the New York Intellectuals and the Frankfurt School. Social theorization was prominent then and US populism’s contingent vulnerability to demagogic exploitation was a major research focus. This article provides an immanent critical reconstruction of these thinkers’ key social-theoretical insights, building to a schematization of ‘modern demagogy’. (shrink)