Political scientists are quite good at predicting 'optimal' policy positions that - under the given circumstances - allow parties to get maximal payoffs in terms of policy, offi ce or votes. What we do not know is whether parties are actually able to take these positions or whether they are constrained to do so. This book attempts to narrow this gap. The major argument is that parties do not choose policy positions from scratch and that they cannot freely change their policy platforms. Rather, voters' lacking perception of changing party platforms and intra-party factors constrain parties when shifting their policy positions. An empirical analysis of party policy shifts in ten Western European democracies shows that these constraints differ across parties and thus affect the parties' position-taking differently. Considering this variation is important to derive more precise predictions for parties' policy platforms and for our understanding of party behaviour in general. "This very good and very important book analyses why (and when) political parties shift their policy positions.Meyer presents innovative empirical analyses and theoretical arguments showing that party policy change is constrained by factors including parties' organisational structures, their governing status, their resources, their previous policy behaviour, the prestige of the party's leader, and voters' levels of political interest. By shifting his focus away from parties' static policy positions and onto parties' policy shifts, Meyer advances our understanding of parties' election strategies and the dynamics of mass-elite policy linkages. This powerful book will help to shape the study of parties and elections for years to come." Professor James Adams, Department of Political Science University of California "This book adds usefully to our knowledge of party behaviour in democracies, to the development of democrative theory and to the assessment of the comparative evidence relating to it. In these ways, it adds signifi cantly to the ECPR book series as a whole and to comparative political science in general." Ian Budge, Professor Emeritus of Government University of Essex