Political Parties in the Legislative Arena: Party Switching and Beyond

Aldo Di Virgilio’s main research interests revolved around the study of political parties as crucial actors in democratic politics. Several of his publications dealt with party organization, party competition, and more recently with party behaviour in the legislative arena, using Italy as a case study. This brief note, which will focus on the party switching literature, will highlight Aldo’s contributions to the study of legislative parties in parliamentary systems.

Research on party switching, that is changes in party affiliation among legislators, has largely to do with the issue of intra-party politics. Indeed, parties are better conceived as “endogenous coalitions” (rather than unitary actors) created by ambitious politicians who aim not to create parties per se, but to be re-elected to control legislative and executive decisions (Aldrich, 1995). The conceptual challenges posed by the study of intra-party politics are summarized in a volume edited by Daniela Giannetti and Kenneth Benoit (2009) which offers an overview of key themes within this area of research, including the nature of party unity and cohesion, as well as of explanations for why parties differ, both within and between national contexts. The contributions in this volume moved the discussion of intra-party politics, which had to a very large degree been focused on the US context, to multiparty parliamentary systems that predominate in Europe. In these systems, party unity is particularly important, as cohesive parties are a necessary condition for the working of electoral democracy. The Giannetti and Benoit (2009) book also set out the theoretical framework associated with the study of party switching.

Party switching has important implications for how well electoral democracy works because changing party affiliation in the inter-electoral period has an impact on democratic accountability, responsibility and representation. The party-switching phenomenon began to attract scholarly attention around 2000 when several articles examining the frequency and rate of party switching in an array of political institutions across countries were published. Case studies ranged from new democracies or weakly institutionalized party systems such as Brazil, Poland, and Russia, to established democracies facing institutional changes and electoral realignment such as Japan and Italy (Benoit and Hayden, 2004; Desposato, 2006; Heller and Mershon 2005; Kato and Kannon, 2008; McMenamin and Gwiazda, 2011; Mershon and Shvetsova, 2008; Reed and Scheiner, 2003; see also Verzichelli, 1996).

A volume edited by William Heller and Carol Mershon (2009) summarized much of the scholarly discussion about both determinants and consequences of party switching. When dealing with determinants of party switching most research focuses on the incentives faced by individual legislators. This work builds on Muller and Strom’s (1999) influential policy-office-votes model of party behavior, as many scholars have adapted it for individual level analyses of legislators’ switching choice. Legislators are assumed to switch parties for three main reasons: (1) policy or ideological motivation where individual legislator’s policy positions are closer to another party rather than their own party; (2) office seeking motivations where legislators evaluate that the prospects of obtaining rewards of office are better in another party; or (3) vote seeking goals so as to ensure their continued electoral survival.

In addition to these motivational hypotheses, the literature highlights the role of institutional arrangements such as regime type, electoral systems and candidate selection procedures in shaping parliamentarians’ incentives to switch their party affiliation. A recent article by O’ Brien and Shomer (2013) provides a comprehensive testing of hypotheses concerning motivational and institutional determinants of party switching in a comparative perspective.

Another focus of analysis has been the timing of switching during the parliamentary cycle. This idea was originally developed by Michael Laver and Kenneth Benoit (2003), who modelled the evolutionary dynamics of legislative party switching between elections. A number of studies has examined how patterns of party switching vary across specific time periods during the legislative term, depending on which payoffs (i.e. electoral, office and policy) are most salient (Mershon and Shvetsova, 2008; Mershon and Shvetsova, 2011).

Party switching has significant consequences for democratic politics. As Laver and Benoit (2003: 215) point out, “there is a great deal of politics between elections. In particular, legislators may defect from one party and join another, parties may split and fuse, and the party system may thereby evolve into one quite different from that produced by election results”. Single episodes may radically change the legislative arithmetic to save the government from collapse or to change political winners into losers, as happened in Italy during the 1996-1998 period (Giannetti and Laver 2001). Moreover, elected politicians’ choices may affect the reshaping of party system during a parliamentary term without the direct involvement of voters in elections (Mershon and Shvetsova, 2013).

Italy has been a laboratory for the study of party switching as this phenomenon became especially important in Legislature XIII (1996-2001) when almost one-in-four Italian legislators changed their parliamentary party affiliation (Heller and Mershon, 2005; 2008). After 2001 legislative party switching declined substantially, supporting the idea that its incidence in the previous legislature could be simply considered as the product of a transition of the Italian party system, triggered by political scandals. However, in subsequent legislatures the number of defections from parties increased once again. Such upsurge in legislative party switching motivated further research. This is where Aldo’s contribution to legislative studies comes into play. Aldo played a leading role in a research team – based at the Department of Political and Social Sciences in the University of Bologna – including myself, Andrea Pedrazzani and Luca Pinto. He was the principal investigator for a project about fluidity in the Italian Parliament. His main collaborator in this research was Luca Pinto. During this work it was quite natural that Aldo became very interested in party switching, as this phenomenon occurred at the intersection of those institutional and political changes affecting the Italian party system in the last decades. These were themes that formed the bulk of Aldo’s research agenda.

The goal of an article co-authored by Di Virgilio, Giannetti and Pinto (2012) was to identify the determinants of party switching in Legislature XVI (2008-2011). This case study was motivated by a puzzle: why a parliament that promised to be marked by stability ended up being characterised by high levels of fluidity? In examining this question, this study adopted the motivational framework described above and added several contextual variables such as timing, party type and party structure.

This article’s two key results are (1) policy tensions constitute one of the main motivations for party switching, and (2) time matters in the study of party switching. The modelling results show that policy motivations are both prominent and constant over time. Moreover, the role of policy motivations of individual legislators in party switching interacts with the degree of ideological heterogeneity within their parties. Within ideologically homogeneous parties, legislators who are relatively distant from their parties’ positions have a greater incentive to switch party. In contrast, within ideologically heterogeneous parties legislators who are closer to their party’s policy position are the most likely to switch due to the party’s limited capacity to effectively pursue policy goals. Coming to the issue of time, this analysis confirms that electoral and office related determinants of party switching have a different impact during the life of a legislature. However, the results about timing were not always consistent with previous research, suggesting that further work was required.

This research has been subsequently extended by Luca Pinto. An article published in 2015 uses a new data set tracking the timing of MPs’ changes in party affiliations between 1996 and 2011 in Italy. Pinto finds that switching is mainly motivated by policy reasons, and that it is more likely during government formation periods and budget negotiations. These results are a consequence of the interplay between legislator’s ambitions and the alternation of key phases in the legislative cycle. This research highlights the fact that party unity is best understood as the output of a complex dynamic process.

An under-developed feature of this work is the importance of factions on party switching by blocks of legislators. Aldo was planning to deal more thoroughly with the distinction between individual switching and coordinated moves leading to party mergers and break-ups that have been a distinctive feature of Italian politics in recent years. The issue of factions was only marginally touched on in another article devoted to examining candidate selection procedures within Italian Parties (Di Virgilio and Giannetti, 2011). Factional politics is the subject of an extensive literature, which cannot be summarized in this short space (however see Boucek, 2012). With regard to the Italian case, this research question has been recently pursued by scholars such as Andrea Ceron (2015) who examined the determinants of factions’ breakaways from 1946 to 2011.

I have no doubt that Aldo would have continued to push forward the intra-party politics research agenda, if his untimely death had not so abruptly interrupted his work. The Comparative Candidate Survey (CCS) project, where both Aldo and Paolo Segatti (University of Milan) were responsible for research in Italy, involved collecting data about individual candidates (and elected representatives) running for national parliamentary elections in many countries. This international research project offers a promising ground to enrich our knowledge of the “internal life” of political parties. Although his collaborators are committed to completing this late research work, it is impossible to replace Aldo. His passing deprives both the Italian and international political science communities of an immensely valued scholar and friend.


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