All regimes require supporters to govern and survive. We discuss the concept of a ‘regime support group’ and present and validate measures from an extensive dataset recording different features of such groups. This Regime Support and Opposition Groups (ReSOG) dataset covers approximately 2,000 political regimes from almost 200 countries, across 1789–2020. Drawing on the knowledge of about 1,000 country experts, we estimate the size and main geographical location of regime support coalitions and key opposition actors. We also map the social basis of regime support coalitions and opponents, using a 14-category scheme covering various social groups. These data provide a unique quantitative history of the social underpinnings of regimes in the modern era. Using them, we show and discuss the broadening of support coalitions over time, especially in autocracies, the rise of major urban groups, and the relative decline of rural elites in politics, globally.
