(iPoster) The Institutional Reshaping of Party Switching in Brazil

• In Event: Poster Sessions: Public Administration & Political Organizations and Parties
  In Poster Session: Poster Session: Political Organizations and Parties

Abstract

In 2007, Brazil's Superior Electoral Court (TSE) established that legislative seats won under proportional representation belong to parties, not individual legislators, creating legal grounds for mandate loss in cases of party switching. The rule was explicitly designed to curb party switching – yet 2022 recorded the highest annual volume of party defections across the seven legislative terms analyzed (1995–2022), with 166 switches in the Chamber of Deputies alone. How can a rule designed to prohibit switching coexist with record-breaking levels of legislative mobility? This paper argues that the party loyalty rule did not fail but rather succeeded in reshaping the strategic landscape of party switching, transforming when and how legislators defect rather than whether they do so at all.

I develop a theoretical framework that treats electoral rules not as absolute prohibitions but as institutional constraints that alter the cost-benefit calculus of political actors. The party loyalty rule created a new judicial arena where parties, substitutes (suplentes), and legislators compete over mandates, but its practical effects depended on how courts enforced exceptions and how actors adapted their strategies. Three mechanisms mediate the rule's behavioral impact: formal safe harbors (party creation, switching windows) that eliminate mandate loss risk; substantive defenses (discrimination, programmatic deviation) that require judicial interpretation; and temporal dynamics that make late-term switches practically immune to sanction given processing times.

The empirical analysis proceeds in two stages. First, I examine how the rule affected the timing of party switching across legislative terms. Using survival analysis on all party switching in the Chamber of Deputies from 1995 to 2022, I compare how long legislators remain in their original parties before and after the 2007 rule. Evidence suggests that the post-fidelity period exhibits a distinctive temporal signature: early-term switches become rare, while defections shift toward the final year of legislative terms. Statistical tests assess that these differences are significant and persist when controlling for party and legislator characteristics.

Second, I analyze how the rule was actually mobilized and enforced through systematic examination of all 155 judicial actions related to party switching involving federal deputies between 2007 and 2022. This analysis reveals that litigation was selective and strategic: only 21.4% of all switches were challenged in court, with declining rates over time. Logistic regression models show that the primary determinants of judicial challenge are the absence of formal safe harbors and sufficient time remaining before term expiration. On the judicial side, the TSE adopted a restrained posture: 45.8% of cases were dismissed without reaching the merits, and only five deputies were ordered to forfeit their mandates, with just one case effectively executed. When the Court did reach the merits, it recognized valid defenses in approximately 80% of cases. Average processing time for forfeiture decisions (612 days) consumed nearly half a legislative term, effectively immunizing late switches from sanction.

The combined evidence suggests that the loyalty rule produced behavioral adaptation rather than deterrence. Legislators learned to exploit formal exceptions – particularly switching windows introduced in 2015 – and to time their defections strategically. Parties, meanwhile, reduced litigation as they recognized the low probability of effective forfeiture. The TSE's restrained enforcement and inconsistent interpretation of substantive defenses further reduced the expected costs of defection, creating an equilibrium in which the rule reshapes rather than prevents switching.

This paper contributes to comparative scholarship on party switching and electoral governance in three ways. First, it demonstrates how judicial rules create strategic opportunities rather than simply constraining behavior, extending rational-choice models of party defection to incorporate litigation dynamics. Second, it provides evidence on how electoral courts may enforce party loyalty rules, an understudied dimension of electoral governance in new democracies. Third, it offers a framework for analyzing the interactive effects of rule design, judicial interpretation, and legislative adaptation that may apply to other institutional reforms targeting legislative behavior. The Brazilian case suggests that evaluating institutional reforms requires attention not only to formal compliance but to the strategic adaptations they induce: reforms may succeed in reshaping behavior even when they appear to fail in preventing the targeted conduct.

Author

• Lucas Herzog, Universidade de São Paulo