In This Article Expand or collapse the "in this article" section Party System Institutionalization in Democracies

  • Introduction
  • Building Democratic Institutions and Its Precursors
  • Concept and Measurement
  • New Parties
  • Party System Collapse and Party Collapse
  • Causes or Correlates of PSI
  • Party Building
  • Consequences of Differences in PSI for Policy Stability and Results
  • Consequences of low PSI for Voters and Electoral Accountability
  • Other Consequences of PSI

Political Science Party System Institutionalization in Democracies
Scott Mainwaring, Fernando Bizzarro, Aaron Watanabe, María Victoria De Negri
  • LAST REVIEWED: 24 September 2020
  • LAST MODIFIED: 24 September 2020
  • DOI: 10.1093/obo/9780199756223-0248


Party systems vary in many dimensions. Variation in the stability and predictability of the party system in democratic elections is captured by the concept of Party System Institutionalization (PSI). Where the party system is stable and predictable, it is institutionalized. Where it is in flux and major new contenders regularly appear, the party system lacks institutionalization. Fundamental differences among party systems revolve around the level of institutionalization. Institutionalized systems make governing easier, lower the probability of populists winning office, promote greater economic growth, and are associated with better public policy. Many scholars who work on Latin America, the post-Soviet region, Africa, and Asia have employed the concept “party system institutionalize” to analyze these regions. Because party systems do not develop in a linear way, in some cases this means the study of deinstitutionalization. When deinstitutionalization happens abruptly, it is called party system collapse or party collapse. The article focuses on PSI, erosion, and collapse in democratic regimes; a different literature analyzes party institutionalization under authoritarian regimes.

Building Democratic Institutions and Its Precursors

The concept of PSI was marginal to political science before the publication of Mainwaring and Scully 1995. Since then, work on PSI and its opposites—erosion (or deinstitutionalization) and collapse—has proliferated. Mainwaring and Scully 1995 refocuses the comparative study of party systems outside of the advanced industrial democracies by emphasizing the importance of institutionalization. Previous works emphasized other dimensions of party systems such as differences in the number of parties or polarization. Mainwaring and Scully 1995 highlights that party systems in the world’s new democracies were in general more unstable, and that parties were usually weaker organizationally, less rooted in society, and seen as less legitimate actors than in the consolidated democracies of the West. They also argued that fundamental differences in how democracy functions revolved around the level of PSI. Two early empirical applications of the concept are the Brazil chapters in Mainwaring and Scully 1995 and Mainwaring 1999, which discuss the Brazilian case at length. Precursors include Sartori 1976, which briefly discusses the distinction between consolidated and nonconsolidated party systems, and Huntington 1968, which argues that differences in institutionalization had major consequences for politics and posits the fundamental importance of parties as a mechanism for structuring politics. Before Mainwaring and Scully 1995, Welfling 1973 uses the concept of “PSI,” without theorizing it.

  • Huntington, Samuel P. Political Order in Changing Societies. New Haven, CT: Yale University Press, 1968.

    Argues that institutionalization is key for political stability and that political stability is essential for good public outcomes. Sees parties as the modern way of organizing politics.

  • Mainwaring, Scott. Rethinking Party Systems after the Third Wave: The Case of Brazil. Stanford, CA: Stanford University Press, 1999.

    Examines Brazil’s post-1985 democratic party system through the lenses of institutionalization. Argues that Brazil had, at that time and historically, a weakly institutionalized party system. Attributes the roots of this weak institutionalization in part to the combination of presidentialism and open-list proportional representation.

  • Mainwaring, Scott, and Timothy Scully, eds. Building Democratic Institutions: Party Systems in Latin America. Stanford, CA: Stanford University Press, 1995.

    Focuses the study of party systems in the developing world on institutionalization. Emphasizes low electoral volatility, strong roots in society, high legitimacy, and strong organizations as the characteristics of institutionalized party systems. Argues that weakly institutionalized or inchoate party systems have profound consequences for democratic politics.

  • Sartori, Giovanni. Parties and Party Systems: A Framework for Analysis. New York and Cambridge, UK: Cambridge University Press, 1976.

    Offers an influential typology of parties and party systems, with a brief discussion of consolidated and nonconsolidated party systems. Concentrates on the number and polarization as the most relevant dimensions in classifying party systems.

  • Welfling, Mary B. “Political Institutionalization: Comparative Analyses of African Party Systems.” Sage Professional Papers in Comparative Politics 4.40–48 (1973): 1–63.

    Applies Huntington’s concept to study party systems in thirty-one African countries. Develops thirteen indicators for the different dimensions of institutionalization, and combines them in an index. Shows that more institutionalized party systems are associated with greater political stability.

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