Uprooted but Stable: Chilean Parties and the Concept of Party System Institutionalization Juan Pablo Luna David Altman ABSTRACT Mainwaring and Scully’s concept of party system institutionalization (PSI) has greatly influenced the literature on parties and party sys- tems. This article contributes to the “revisionist” literature on PSI by exploring the recent evolution of the concept’s four dimensions in Chile. It finds that the Chilean party system is not homogenously institutionalized (as conventionally argued) but is simultaneously frozen at the elite level and increasingly disconnected from civil society. In this regard, it approaches some recent descriptions of the Brazilian party system, a prototypical example of an “inchoate” party system that has gained stability over time without developing roots in society. This article argues that the current operationaliza- tion of the concept of PSI is problematic. Not only should all four dimensions of the concept be simultaneously measured, probably through multiple indicators for each one, but their trends across time and space should also be better integrated into the concept’s theoretical structure. M ainwaring and Scully’s concept of party system institutionalization, first published in 1995, has greatly influenced the literature on par- ties and party systems, to the point where it has become the established approach for comparative analyses of developing countries. Conceptu- ally, Mainwaring and Scully (1995) identify four dimensions of party system institutionalization (hereafter PSI): a. the stability and regularity of party competition patterns b. the presence of party roots in society, which helps to create the stability of institutionalized systems c. the relative level of party legitimacy in society d. the presence of well-developed party organizations, as opposed to parties that function as electoral vehicles for personalistic leaders Mainwaring (1999) explicitly conceptualizes the relationship between the four dimensions of PSI as positive and linear, arguing that high levels of PSI in one dimension usually correlate with high levels in the other three (1999, 27). Accordingly, the concept has been conven- © 2011 University of Miami