The crisis of social democracy has been the subject of numerous articles and books from different fields such as party politics, political sociology, and political economy. This article contrasts two competing explanations prevalent in the related literature. According to the postindustrial dilemmas hypothesis, the crisis of social democracy is the inevitable result of the transition from industrial to postindustrial society and the electoral trade-offs social democrats are facing as a consequence. The neoliberal contamination hypothesis instead emphasizes social democracy’s neoliberal turn and the resulting loss of trust in social democracy, especially among working-class voters. It is argued that both hypotheses are not only based on diverging conceptions of partisan politics, pitting Downs against Gramsci, but also on different theories of capitalist development (modernization theory vs Polanyian “double movement”). As a result, each explanation captures important aspects of the current crisis of social democracy but also misses other aspects that are essential to fully understand this phenomenon.