The publication of Müller and Strøm's edited volume is timely because there has been a growing feeling in the literature that the time has come to move on. It has always been the case that, when analysts have applied formal models to real-world examples, they have explained anomalies by acknowledging motivations that go beyond those in their models. Thus the refusal of Communist or Green parties to converge on the center ground may be excused in vote-maximizing models of party competition on the ground that they are policy seekers. The willingness of ideological strange bedfellows to get into coalitions with each other may be explained in policy-driven models of government formation by the assertion that these particular parties care much more about getting into office than about enacting their policy program. Increasingly, these observations are leading theorists to try constructing models in which politicians have multiple motivations, which they must typically trade off against each other when making hard choices.

It is one thing to write down a model containing such trade-offs. It is quite another to apply it to the real world, an exercise that requires the analyst to provide at least a ballpark estimate about how a particular politician might trade off such-and-such a probability to getting into office against such-and-such a dilution of fundamental policy objectives. If my model tells me that you can increase your probability of being in government by 40% if you drop your long-standing policy objective of nationalizing the commanding heights of the economy, how do I know a priori whether or not you will do it? I need some realistic information about how you trade off office and policy motivations.

Müller and Strøm have provided us with the first book-length empirical study of precisely this problem. Essentially it is an edited collection of thickly descriptive case studies, topped and tailed by general chapters by the editors in reviews that are sensitive to a range of the theoretical implications of this material. They set the scene in an opening chapter that does not contain a model or even a typology of trade-offs and hard choices, but that sets out to clear away some of the conceptual underbrush entangling these—a task that necessarily precedes the construction of such a model. We then have 10 case studies written carefully by well-established experts in their fields. Each of these takes a particular set of hard-choice trade-offs in a particular country, providing a detailed post hoc interpretation of this. The countries covered, in chapter order, are Ireland, Denmark, Spain, The {Netherlands,} Italy, Austria, Norway, Germany, Sweden, and France. This book was a long time in the making and the case studies are not wildly up-to-date, but that is not the point in this instance. What the case studies do is use a lens fashioned by the editors to throw serious light, pretty much for the first time, on the real-world trade-offs and hard choices that will be of critical importance to theorists who want to construct improved models of party competition based on more complex sets of motivational assumptions.

There is no space here to go into detail on the substance of each case study, but it should be said that the authors of the case studies have a sure touch with the detail of their material that should inspire confidence in those who might wish to build on these foundations. The main virtues of this book are thus the astute way in which the editors have identified a theoretically important matter that requires a preliminary empirical survey and the professionalism with which the authors of the case studies have set about their tasks. This is thus essential reading for those who have ambitions to build more complex models of party competition. It is also an attractive supplementary text for those teaching courses on party competition.