Socialism is typically portrayed as a deeply populist doctrine, yet it often has difficulties reconciling populism with more centrally socialist ideals. As a result, populism is both a consistent preoccupation and a recurring problem for socialists. This chapter traces these shifting tensions through three episodes in socialism’s development: the works of Karl Marx, Auguste Blanqui, and Eduard Bernstein. Each manifests the tensions in complex and subtle ways. Ultimately, the contemporary forms of social democracy that have descended from this heritage provide the means for a potential reconciliation, establishing the material conditions for a radically populist politics.