Do political parties fulfil their election mandates? This study provides an empirical analysis of a question many people feel they already have an answer to. The extent to which parties talk about similar issues and take similar positions before and after elections is studied in the context of the United Kingdom and the Netherlands. The main question is whether the different institutional structures in these countries lead to differences in mandate fulfilment. To answer this question, this book provides an analysis of parties’ election manifestos and parliamentary debates. It shows how the political competition changes after elections. It analyses differences between government and opposition and the impact of issue saliency and policy position extremism. Moreover, it provides an overview of mandate fulfilment since the 1950s: has party mandate fulfilment declined?