Cities, and the process of urbanization more broadly, play an integral role in narratives and theories of political change, from revolutions to democratization. Yet most accounts fail to make clear distinctions between the political implications of (i) population concentration (spatial context effects), (ii) socioeconomic change in cities (demographic composition effects), and (iii) increases in the size of urban populations (scale effects). These distinctions are significant in the post-WWII context, which has seen rapid “urbanization without growth” in many low- and middle-income countries. We argue that cities facilitate political activity through spatial effects, tend to have populations biased in favor of democracy due to compositional effects, and that these effects have scalar properties—i.e. they increase with city size. Analysis of World Values Survey data from over 179,000 individuals across 95 countries and cross-national regressions analyzing determinants of political change since 1960 in 161 countries are consistent with this theory.