The paper addresses the issue of how the notion of common or public weal can be specified for a democratic polity as a ,,cooperative venture for mutual advantage“ (Rawls). It is argued that common weal in democratic politics is to be understood as its capacity to produce mutual advantages for the citizenry and that the measuring rod for this capacity is citizen sovereignty, i.e. the responsiveness of democratic politics to citizens‘ common interests. Subsidiarity is analyzed as an organizational principle in politics that can serve as an instrument for advancing citizen sovereignty.