When, why, and how are democratic institutions reformed? This is the broad question guiding this research, rooted in a context of declining political support in Western Europe. This book deals with the context, the motives, and the mechanisms explaining the incidence of institutional engineering in consolidated Western European democracies between 1990 and 2015. It is centred on the choice of elites to use—or not to use—institutional engineering as a response to the challenges they face. The book answers two key questions about institutional change. First, how much change to the core democratic rules can be observed over the course of the last twenty-five years, where did change take place, and at what point in time? Second, why are some reform attempts successful while others are not? The use of a wide comparison of Western European democracies over time is the central contribution of the book in tackling these two issues. This enables a development of the concept of bundles of reforms, a key analytical tool to understand institutional change in a longitudinal and comparative perspective.