Clientelism is the exchange of goods and services for political support, often involving an implicit or explicit quid-pro-quo. Clientelism involves an asymmetric relationship between groups of political actors described as patrons, brokers, and clients. Although many definitions for clientelism have been proposed, according to the political scientist Allen Hicken, it is generally thought that there are four key elements of clientelistic relationships: Contingency and iteration are the two components shared across most definitions of clientelism.