Revisiting the inclusion-moderation thesis in the context of decentralized institutions: The behavior of Indonesia’s Prosperous Justice Party in national and local politics

Institutions figure prominently in explanations for why radical parties forego their agendas and subject themselves to democratic principles when included in politics. Analyzing the Prosperous Justice Party’s political trajectory across Indonesia’s multi-level government structures between 1999 and 2009, I show that the Islamist party has gradually adopted more moderate behavior not only in national politics, where institutional incentives are conducive to moderation, but also in local politics, where institutional incentives for moderation are weaker. The absence of a strong pattern of invariant association between institutional incentives and the moderation of party behavior points to the importance of party internal mechanisms in moderation processes. Based on primary sources and in-depth interviews with party members, I argue that socio-structural factors shape a party's internal power dynamics and thereby its long-term capacity to adopt more moderate behavior.