Understanding Intra-Party Organization in Multilevel Countries: Vertical and Horizontal Decentralization

This paper examines how political parties define their internal organization in the context of a multilevel territorial decentralization. We challenge deterministic accounts that treat party decentralization as an automatic response to state structures. Instead, we advance a framework that explains variation along two dimensions of internal change: vertical decentralization (the diffusion of decision-making authority) and horizontal decentralization (the scope of regional organizational development). Our argument builds on the path-dependent features of a party’s genetic model (Panebianco, 1990). First, a party’s initial vertical and horizontal configurations are based on its dominant coalition at the time of its foundation. This establishes the structural baseline upon which external pressures operate. On the one hand, institutional isomorphism encourages parties to develop substate structures that mirror the territorial distribution of state authority, producing organizational regionalization. On the other hand, parties face electoral incentives to adapt their organizations to capture subnational offices. Yet these external pressures do not generate uniform redistributions of internal power. We hypothesize that intra-party decentralization varies systematically across both dimensions. Vertical decentralization -the actual transfer of decision-making authority -is not automatic. Instead, meaningful shifts occur only when central elites make strategic choices in response to contextual pressures, such as critical regional elections or coalition demands, consistent with organizational responses to external shocks (Harmel and Janda, 1994). Horizontal decentralization, by contrast, remains bounded by a party’s genetic trajectory and the territorial configuration of the polity. This paper reviews the existing literature and proposes an analytical framework for understanding party organization in multilevel states. We test our argument through a cross-country comparison using data from the Party Politics Database (PPDB). Our analysis proceeds in four steps: we begin by critically reviewing the existing literature, then develop a theoretical framework, followed by a map of cross-national differences along the vertical and horizontal dimensions, and finally assess how institutional and contextual factors account for this variation.