Within the literature devoted to the study of political parties, scholars have recently directed more attention towards intraparty dynamics. The ‘party as a unitary actor’ assumption seems to have withered away in the last decades. The party is increasingly viewed as a heterogeneous entity, in which dissenting attitudes are frequent. Yet the causes of intraparty dissensions remain quite obscure. This dissertation aims at providing a better understanding of the causes of dissent within parties, especially within parliamentary party groups. <p><p>Intraparty conflicts, dissent or ‘voice’ phenomena have been studied through different literatures that have developed independently from each other: studies dealing with party factionalism, social-psychological and economic theories of organizations (e.g. Hirschman’s trilogy of exit, voice and loyalty), and legislative studies dealing with parliamentary party voting unity. The dissertation attempts to (re)conciliate these separate literatures, and shows how legislative studies, factionalism literature and theories of organizations can help to rethink the concept of dissent, and to grasp why parliamentarians are more or less likely to dissent from their party line. <p><p>The dissertation defines dissent in the parliamentary party as a two-dimensional concept, and operationalizes it as the MP’s frequency of disagreement with her/his party and the MP’s attitude of (non)loyalty in case of such disagreement. At the theoretical level, the dissertation draws on several theoretical approaches –institutional, rational and sociological– and formulates a broad set of hypotheses linking system-, party- and individual-level factors to these two dimensions of dissent. At the empirical level, the dissertation analyzes the causes of dissent within parliamentary parties in a comparative perspective. The analysis examines parliamentarians’ attitudes across 15 European national parliaments and tests the hypotheses formulated in the theoretical part by using the PARTIREP MP Survey dataset. <p><p>The results first show that, while European parliamentary parties are usually viewed as united blocks in terms of voting behavior, looking at MPs’ attitudes provides a more nuanced picture: European parliamentary parties show important variations in their MPs’ frequency of disagreement and attitudes of non-loyalty. Among the factors that explain these variations, both institutional (electoral rules, state structure, effective number of parties, intraparty organization) and sociological (gender, age, socialization, ideological preferences) factors need to be considered. In addition, the research shows that the two dimensions of dissent, though they are connected by a sequential relationship, should be studied distinctly, as different factors affect them respectively. The frequency of disagreement is best explained by the MP’s gender and previous elected office at a lower level than the national one, by the ideological distance between the MP and her/his party’s position in interaction with the party ‘family’, and by intraparty organizational factors (candidate selection procedures and EPO-PPO power balance). Non-loyalty depends more on the institutional structure (multilevel vs. unitary state, ENP) and on the candidate-centeredness of the electoral system; but is also affected by individual-level factors (age and length of incumbency) and by the party ‘family’. On the whole, by contrast to what is usually argued, ‘the party’ matters’ in determining the level of intraparty cohesion: the impact of intraparty organizational structure and party ideology or family is determinant, but more research is definitely needed in order to disentangle the ‘organizational’ vs. the ‘ideological’ effects.<p> / Doctorat en Sciences politiques et sociales / info:eu-repo/semantics/nonPublished