Generations of political scientists seek to understand the relationship between citizens' democratic values and democratic stability. The key premise of this research tradition is that democratic societies live on a ‘social consensus’ over a set of democratic values; a democratic norm. Yet, until today scholarship has neither carefully theorized the role of nor measured this social consensus. Building on research in social psychology, we conceptualize democratic norms as social norms: citizens may think that most people in democracies support its institutions (descriptive norm) and also that one ought to do so (injunctive norm). Based on this, we provide a theoretical framework and derive observable implications of which country- and individual-level characteristics structure social democratic norms. Using existing surveys and large-scale original survey experiments, we will then measure these democratic norms in up to 15 democracies. Our research has important implications for research on democracy showcasing the role social norms play to craft democratic support in our societies.