This article studies the phenomenon of clientelism as an informal institution and poses the question of its persistence in relation to subnational political regimes. A case study was done in the province of Santiago del Estero in Argentina, taking as its starting point the everyday activity of politicians in different elected offices. It showed that, while provincial politicians' main resource for attaining power is political capital in a territory, once in power, above and beyond their formal attributions, they must act as mediators between their territorial bases and the public administration. Clientelism as an informal institution is imposed upon whoever seeks to accumulate and conserve political power in the province.