This chapter develops an explanatory model of regime support applicable to both democracies and autocracies. The explanatory model includes both individual- and system-level determinants and explicates how these interact in shaping regime support. On the individual-level, it integrates culturalist and institutionalist explanations of support to arrive at five central sources of regime support: political value orientations, societal value orientations, incumbent support, democratic performance evaluations, and systemic performance evaluations. On the system level, it draws on social psychological theories of attitude formation and identifies four sources of regime support: macro-cultural context, macro-political context, actual systemic performance, and level of socioeconomic modernization. Recurring to the fundamental differences between democracies and autocracies, the explanatory model expects the individual-level processes forming regime support to be universal across regime types, but effects of system-level sources of regime support to vary between democracies and autocracies, due to indoctrination and propaganda distorting the attitude-formation process in autocracies.