The article proposes a systems-theoretical approach to political clientelism. It places political clientelism in the theoretical framework of a democratic political system characterized by internal differentiation in government and bureaucracy, party politics and a politically relevant public. Against the background of existing research on the link between democracy and political clientelism, it uses Luhmann’s concept of power and more specifically his model of the formal and the informal power cycle to point out parallels and differences between a political system based on expectations with regard to policies and a political system in which clientelistic expectations prevail. Democratic political systems are based on formal, legally codified power and informal power. Clientelistic power is a special form of informal power affecting this interplay, as the example of democratization in Mexico shows. Political systems with clientelistic expectations differ from those with a policy orientation with regard to the complexity of policies, the generalization of political support, the bases for personalization, the pattern of interest articulation and the most prominent external influences on the system.