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The Politics of Polarization: Legitimacy Crises, Left Political Mobilization, and Party System Divergence in South America


The rise of the left across much of South America in the aftermath of market reforms catalyzed a major divergence in regional party systems. In some countries, polarizing party systems emerged, marked by conflictual patterns of contestation between major political parties and the politicization of class cleavages in party competition. In other countries, integrative party systems consolidated, characterized by largely consensual patterns of competition and class cleavages that remain unexpressed in party competition. This variation in party systems represents a critical macropolitical legacy to emerge from the tumultuous recent decades and offers fruitful ground for developing and testing theory regarding the causes of political and social polarization in the younger democracies of the highly unequal developing world.

Examining the cases of Venezuela, Brazil, and Chile, this dissertation develops an argument that centers on the avoidance or occurrence of "legitimacy crises": anti-systemic episodes involving protracted failures of governance and steep erosions of public confidence in state institutions. The presence or absence of legitimacy crisis decisively shaped factional contestation within the partisan left in each country, leading to party system divergence along two dimensions. Whether radical or moderate left coalitions consolidated entailed the establishment of conflictual or consensual patterns of contestation within party systems. Once in office, the radical and moderate left also pursued different strategies of political mobilization - mass-organizational in Venezuela and catchall in Brazil and Chile - that subsequently drove variation in the translation of class cleavages into party competition.

The study relies on a variety of qualitative and quantitative data sources, including those gathered during 11 months of fieldwork in Venezuela, and utilizes both process-tracing and statistical methods (primarily genetic matching) to draw causal inferences. A concluding chapter shows that the argument can also explain variation in party systems in two other countries where the left has taken power (Bolivia and Uruguay), suggesting that the framework in the study might provide a broader model of macropolitical divergence in the region during the last decades.

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