Intra-party diversity challenges parties’ ability to reach internal consensus. Members from differing geographic regions hold competing preferences over solutions to local problems. These differences manifest in disagreements over the powers for regional governments, particularly in unitary states with devolved powers. We propose that parties incapable of managing an internal consensus on prominent issues such as devolution will attract less electoral support from regions with distinct independence movements. To test predictions from this perspective, we combine supervised analysis of speeches from party national conferences in the UK with survey evidence from the British Election Study to predict voters’ support for national parties in devolved settings. We use supervised machine learning approaches to estimate differences in preferences over regional powers using a new dataset and corpus of party conference speeches from the UK 1997 – 2018. The primary analysis estimates regional differences in intra-party support for devolved powers with data on public opinion. We expect to find that when the national UK parties disagree over regional issues that Scottish and Welsh voters will be less likely to vote for them and perceive the parties as more divided. The results from will provide evidence to evaluate a theory of intra-party decision-making and support for institutional reform and demonstrate the usefulness of supervised approaches for studying intra-party politics.