PSX0010.1177/0032321716634094Political StudiesItzkovitch-Malka and Hazan 634094research-article2016 Article Political Studies 2017, Vol. 65(2) 452 –474 Unpacking Party Unity: © The Author(s) 2016 Reprints and permissions: The Combined Effects sagepub.co.uk/journalsPermissions.nav https://doi.org/10.1177/0032321716634094DOI: 10.1177/0032321716634094 of Electoral Systems and journals.sagepub.com/home/psx Candidate Selection Methods on Legislative Attitudes and Behavioural Norms Reut Itzkovitch-Malka1 and Reuven Y Hazan2 Abstract This article analyses the effect of electoral systems, candidate selection methods and the interplay between them on individual legislative attitudes and behavioural norms, specifically on two facets of party unity: party agreement and party loyalty. Our main argument is that one must take into account the effect of inter- as well as intra-party competition, and the interaction between the two, in order to explain individual legislative attitudes and norms. Using data from 34 European parties across 10 countries, we show that under exclusive candidate selection methods, there are large differences between proportional representation and single-member district electoral systems in their effect on party agreement and party loyalty. Under inclusive candidate selection methods, however, such differences are much less apparent. In other words, the candidate selection method conditions the influence of the electoral system on legislative attitudes and behavioural norms. Keywords electoral systems, candidate selection, party unity Accepted: 14 January 2016 Introduction This article empirically tests the combined effect of electoral systems (inter-party compe- tition) and candidate selection methods (intra-party competition) on legislative attitudes and behavioural norms. We focus on two facets of party unity: party agreement – defined as the extent to which co-partisans share similar policy preferences with one another 1The Open University of Israel, Ra’anana, Israel 2The Hebrew University of Jerusalem, Jerusalem, Israel Corresponding author: Reut Itzkovitch-Malka, The Open University of Israel, 1 University Road, POB 808, Ra’anana 43537, Israel. Email: [email protected] Itzkovitch-Malka and Hazan 453 when voting on legislation – and party loyalty – defined as the extent to which legislators subscribe to the norm of party unity in the absence of such shared preferences. The aca- demic literature has yet to address this two-dimensional approach empirically, moving beyond explanations of legislative attitudes and behaviour that only rest on the influence of electoral systems. We argue that the candidate selection method conditions the effect of the electoral system on legislative attitudes and behavioural norms. Under exclusive candidate selection methods, we will see substantial differences in party agreement and loyalty between legislators elected by proportional representation (PR) electoral systems and those elected by plurality/majority single-member district (SMD) electoral systems. On the contrary, under inclusive candidate selection methods, such differences will shrink and legislators elected by both systems will resemble each other much more regarding party agreement and party loyalty. Using attitudinal data from the PARTIREP1 project on elected representatives in 15 countries, combined with data collected on candidate selection methods in 34 European parties in 10 countries (for a full list of the countries and parties included in this research, see Appendix 1), we are able to show that the candidate selection method and its charac- teristics condition the effect of the electoral system on party agreement and loyalty. More specifically, when the party leadership controls legislators’ chances for reselection, we find substantial differences in the effect of the electoral system on party agreement and loyalty: legislators elected by party-focused PR electoral systems demonstrate higher lev- els of party agreement and loyalty compared to legislators elected by candidate-based SMD systems. However, when the party leaders do not control the nomination process, the type of electoral formula has a much smaller influence on legislative attitudes and behavioural norms. Party unity is conceptualised in this article as an end result of the legislators’ sequential decision-making process. That is, we do not examine the final outcome – legislators’ vot- ing behaviour – but rather focus on legislators’ pre-floor attitudes: party agreement and party loyalty. By doing so, we follow an increasing number of scholars and studies who adopt the attitudinal approach to the study of party unity (Andeweg and Thomassen, 2011; Kam, 2009; Krehbiel, 1993). The reason for this is first and foremost theoretical: party unity can be the result of many different mechanisms, which cannot be bound together in a uniform way (which is what we do when we only look at the final outcome). Unity can be the result of legislators’ shared preferences (party agreement), of a voluntary subscrip- tion to the norm that legislators should toe their party line even when they personally disa- gree with it (party loyalty) or of the use of involuntary disciplinary instruments by the party leadership (party discipline). While the end result in all of these cases is the same voting unity, the intra-party dynamics leading to it can vary dramatically. Clearly, the dynamics in a party where there is high party agreement is different from the dynamics in a party whose legislators lack party agreement but possess high levels of party loyalty; and these dynam- ics are very different from those in a party whose legislators lack both party agreement and party loyalty, thus requiring discipline. This changes the atmosphere within the party, the dynamics between co-partisans and, most importantly, the nature of the relationship between the party leadership and its members of parliament (MPs). Therefore, it is impor- tant to flesh out these processes and analyse the factors affecting them. Following that, we cannot claim that institutions, such as the ones studied in this article, affect party unity directly. On the contrary, we claim that institutions do not affect voting behaviour directly; rather, they influence the legislators’ decision-making process in determining whether to cast their vote with their party or against it. 454 Political Studies 65 (2) But there is also an empirical reason for our decision to use attitudinal data on party unity. While the legislators’ voting behaviour is heavily constrained – West European parliamentary systems provide very little variance in party unity (Carey, 2009; Depauw and Martin, 2009; Heidar, 2006; Sieberer, 2006) – their attitudes and norms of behaviour regarding party unity are far less constrained and present much more variance. In order to overcome the no-variance problem we face, we can investigate party unity – both as it is perceived by the legislators and how it exhibits itself in the legislature – by conceptualis- ing it as a sequential decision-making process. Hence, while this research does not address legislators’ actual voting behaviour, it provides an understanding of the inner processes legislators and parties undergo before a legislator’s vote is cast in the plenum. Background Almost any prospective or incumbent politician in any country must pass two barriers, not one, in order to become an elected representative – they must first be chosen by a party selectorate, be it a party elite or the party members, and only subsequently be elected by the voters. Each of these two barriers can vary in relevance and in nature – each can be either more personal or more under party control – but both are present, both are signifi- cant and both must be taken into account if we want to understand legislative behaviour. The second barrier, the electoral system, has received a plethora of scholarly attention, producing numerous studies of its diverse effects on politics in general and on the legisla- tive branch in particular.2 However, the first barrier, the candidate selection method – and especially its influence on legislative behaviour – remains largely disregarded by the academic literature and has only recently begun to attract scholarly attention (Alvarez and Sinclair, 2012; Hazan and Rahat, 2010, 2006; Katz and Cross, 2013; Narud et al., 2002; Rahat and Hazan, 2001; Tavits, 2008, 2005). In other words, most scholars attribute leg- islative behaviour to the way legislators are elected by the general public, and not to the way they are selected by their parties. Since electoral systems shape the conditions under which legislators compete for re-election, they are expected to affect both party agreement and party loyalty, depend- ing on the candidate-centred versus party-based nature of the system (Van Vonno et al., 2014). While the majority of the literature finds the ballot structure to be the key char- acteristic in shaping the candidate-centred versus party-based nature of the electoral system, there are studies that emphasise the importance of the electoral formula and the district magnitude in shaping it. For example, a recent study on how electoral systems affect legislative behaviour in France, Portugal and Belgium found that of the three main characteristics of the electoral system, the most influential on the constituency versus party focus of representation among legislators is the electoral formula. ‘When “representing district/region” versus “party” are compared, majoritarian systems with SMD,