A Unified Theory of Party Competition “integrates the perspectives of spatial modeling and behavioral research” (p. xvii). It does so by expanding the usual set of assumptions that underlie spatial models, and by accounting for various aspects of voters' electoral behavior. Choices of campaign strategies by party elites, their decisions of what to propose to the voters, are directed toward the same objective as in the tradition growing from Anthony Downs's (1957) An Economic Theory of Democracy—maximization of the vote that they receive in an election. When pursuing this goal, however, parties confront a richer environment of voters' preferences than spatial theorists customarily assume. James Adams, Samuel Merill, and Bernard Grofman take the Downsian criterion—policy distances between the voter and a party—as but one weighted component in the electors' utility functions. Other factors that compel a voter to support a particular party and which the authors include in order to incorporate “the full diversity of measured influences on the vote” (p. 228) are “partisanship, retrospective economic evaluations, and sociodemographic characteristics” (p. 228). Anticipating that the voters will choose with more than just the policy distances in mind, parties find themselves diverging in policy space as they compete for the vote. Thus, a more realistic set of behavioral assumptions with regard to the voters leads to more reasonable predictions for the location of party platforms than the convergence result characteristic of most spatial models. This furthers the authors' objective to improve the quality of the contribution of the spatial modeling literature to our understanding of the rationale behind the ways in which party systems are arranged in the world's democracies.

As the book sets out to integrate rational choice and behavioral approaches to the study of party competition in elections, a necessary step to achieving such integration is the merging of the corresponding methodologies of analysis. There is no question that this distinguished set of authors endeavors to bridge the two approaches while departing from the rational choice tradition. In fact, they succeed in showing the reader the method by which rational choice can be useful, helpful, and sensible as a tool for modeling the real-world complexity of politics. The authors strive for the “right” model of electoral parties—the one that does not assume away any of the important considerations in the political process. Then, once the “unified” model is in place, they use the data to estimate the values of its parameters, and then solve for the case-specific predictions of parties' equilibrium strategies. They go to great lengths to produce empirical specifications that are functionally equivalent to predicted equilibrium party strategies generated by the analytical model. This allows a direct assessment (as opposed to one through the distantly related partially testable implications) of the consistency between their formal model and the actual observed competitive behavior of parties.

In addition to the analytical value of the unified model and the applied electoral analysis, the field will take from this book several important lessons. First, it is quite possible to build a formal theory on a set of palatable and empirically based assumptions. Second, at least when the equilibrium of the resulting game is unique, one could observe whether parties' actual behavior in the political process is consistent or inconsistent with the computed strategies. Third, though the same general theory may apply to many cases, the actual game will always be case specific and unique to a given set of circumstances. The general theoretical model is good for asserting the existence and uniqueness of the equilibrium. But it is counterproductive to look for empirical and cross-national validation of equilibrium predictions obtained from a generic set of parameters, since equilibrium results may move around substantially depending on the specific parameter combinations. Instead, an appropriate test of the general theory is in finding that its applications—parameter-specific formulations of the basic game, supplemented with additional game components appropriate in a given setting but not in others—generate equilibrium predictions that match the observed behavior of the parties. The general model “travels” well when, applied to many different specific settings, it produces specific predictions that are consistent with actors' actual observed behavior in those settings.

The Logic of Pre-Electoral Coalition Formation opens with a statement of fact: Preelectoral coalitions among otherwise distinctive political parties are a frequent occurrence in electoral campaigns. While many strategic aspects of electoral competition have been extensively studied in the literature, this book is filling the niche that was largely unoccupied until now, by offering a prospective model of strategic preelectoral coalescing by parties and by testing the resulting hypotheses with the author's original data set on preelectoral coalitions in stable parliamentary democracies. Sona Nadenichek Golder's main objective is to extend the spatial theory of political competition to include the choice of entering into a preelectoral alliance. Her central argument is that, indeed, spatial considerations weigh heavily in the rationale behind the coalition formation, though considerations of dividing offices among the partners are also profoundly important.

Why and when do preelectoral coalitions form? What compels parties to jointly appeal for the voters' support? And, turning the issue around, if they do better seeking the vote together, why would they still elect to maintain their distinctiveness in platforms and organizations? The book takes the reader all the way from the formal model of the game of party coalescing, through the in-depth case studies of party agreements in France and South Korea, and to the large-n testing of a set of hypotheses with an original data set that, for the most part, is also included in the book. For a preelectoral coalition to be deemed advantageous by its prospective participants, there must be a considerable policy threat from the opposition victory (large spatial difference in platforms), close compatibility between the programs of the prospective partners, a substantial improvement in the probability of winning with the coalition as compared to without, and a good prospect of divisibility of the resulting spoils, such as cabinet portfolios or other offices and office-related benefits.

Case studies of interparty coalescing in France and South Korea nicely highlight the main intuition of the formal model, illustrating the role of policy distances from the opposition and within the coalition itself, as well as the impact of the expectations for winning alone versus jointly. Cases lead one to conclude that coalitions are more likely to be formed and appear earlier in the electoral process in parliamentary than in presidential elections, because, the author argues, the office benefits in the latter are nondivisible. At the same time, the detailed accounts of interactions among the partisan players in the circumstances leading up to specific elections in these countries serve to enrich the picture that the theoretical chapter sketches for the reader. The author is knowledgeable and insightful, and the empirical hypotheses that she puts to a large-n test are no less rooted in the thorough examination of her main cases than they are in the abstract game-theoretic model.

Empirical analysis is based on the data set of 293 parliamentary elections in 20 developed parliamentary democracies. (Considering that the case studies indicate that a presidency impedes coalescing among the parties, the reason for not including presidential regimes in the data probably warrants more of a justification.) With her data set, the author estimates the chances of coalition formation for any given party with any other party that runs in the same election, seeing her hypotheses borne out.

Another question to the author is of a theoretical nature. Would her formal model of preelectoral coalition building be similarly applicable to describing the phenomenon of the preelectoral party formation? How could one capture the principal difference between forming a coalition and forming a party, that a coalition is precisely when, despite the advantages of running together, participants keep separate for the future, maintaining their distinctive political identities and organizations? If the decision to coalesce is driven by the goal to win enough votes to get into the parliament, and thus depends on the rules for winning and the range of offerings supplied by other competitors, then so is the decision to merge into a single party, or to campaign on a particular electoral platform. If there is one thing that I would ask the author to add, it is to draw a clearer line between when one expects to see coalitions as opposed to parties—in formal and empirical analysis.

In sum, Golder's book is a fascinating, fresh look at preelectoral strategy of interparty coalition formation. It is a timely and useful contribution, and a strong voice in the party systems literature. Both of these excellent books signify the continued usefulness of the spatial approach for understanding elections and parties, and show how spatial theory can serve as a neutral platform for adding on other analytical components that we believe to be similarly relevant in determining election results.