Intra-Party Diversity as Stratarchy: An Electoral and Organisational Explanation of Party (Lack of) Cohesion

What can account for ideological diversity among MPs from the same parliamentary party? While the main works focusing on party-MP relations have pointed out the role of electoral systems in explaining party cohesion, we propose that MPs’ distance to their party can mainly be explained by political parties’ organisational characteristics, defined by a series of vertical bargains between the national and the local level. The allocation of power between the different party units affects the legislator’s ideological position. Other factors, such as constituency pressure or MPs’ personal characteristics, affect intra-party variations among legislators through the mediation of these vertical bargains