The literature that explores the relationship between decentralisation and the structure of the party system has barely explored an important dimension of party integration, namely the degree of ideological cohesiveness among parliamentary elites. This paper purports to fill the literature gap by analysing heterogeneity in attitudes towards devolution among representatives from Spanish state-wide parties (the People’s Party (PP) and the Socialist Party (PSOE)). Drawing from a sample of 460 parliamentary elites, results show that within-party variation in preferences towards regional self-rule are accounted by the territorial cleavage (historical regions vs ordinary ones) as well as by an institutional cleavage, defined by the type of assembly – regional or national – in which representatives are elected. However, parties’ political and organisational trajectories moderate the impact of those cleavages: territory prevails in accounting for internal variation within the PSOE, whereas the institutional cleavage is more important to explain internal cohesiveness among PP’s party elites.