As the highest-ranking officials of their parties, leaders fulfill prominent roles in politics. They shape their parties' policy positions, take on the highest executive offices when in government, and become the most vociferous critics of governments when in opposition. Party leadership selection is typically a widely reported party event, and leaders provide a public face for their parties come election time. The role of party leaders has therefore been at the center of numerous studies examining how leaders' personal traits impact vote choice. Whereas previous studies have tackled this question by focusing mostly on particular countries or specific elections, Platform or Personality? offers a broader cross-national and longitudinal perspective using an impressive data set assembled from election studies from seven countries. In short, Amanda Bittner's answer is that leaders' traits matter, but that not all traits are equally important and not all leaders are evaluated according to the same criteria. In particular, the results suggest that voter evaluations of leaders' character seem more important than those of leaders' competence.

The author organizes the book into eight chapters. Following the introduction, Chapter 2 offers a thorough and useful overview of available data on party leader evaluations in more than 100 election surveys. The author convincingly demonstrates that a sufficient number of studies exist with similar closed-ended questions for a pooled analysis. In total, 35 election studies across seven countries over a 40-year period form the basis for the analysis. Chapter 3 introduces competence and character as the two dimensions that define the personality traits of leaders. These are identified using pairwise correlation analyses of 55 trait questions for major conservative and center-left party leaders (and 34 for leaders from parties that include the smaller left ones). To enable a pooled analysis, Bittner recodes all trait evaluations on a common 0–1 scale, with a value of 1 reflecting the most positive evaluation for a given leader. The consequences of doing so, however, are not entirely clear due to the different answer formats in the surveys, and a more careful discussion of the data would have been useful. For example, while some questions ask for a leader rating on an ordinal scale, others simply ask whether a particular trait applies to a leader or not. It is conceivable that pooling the data this way introduces variation simply as a result of various answer formats of the trait evaluation questions.

The next chapters investigate the data. Chapter 4 examines voters' ratings of leaders on the competence and character dimensions. The author finds that partisans of all parties give the highest ratings to their own leaders, but that voter ideology and issue attitudes further affect the evaluations. Sociodemographic characteristics of voters, on the other hand, play a minor role. Building upon this analysis, Chapter 5 additionally considers the impact of the party label of leaders. Bittner shows that voters rate leaders according to partisan stereotypes: After their own party leaders, partisans perceive leaders from left parties positively on the character dimension, but conservative leaders positively on the competence dimension. The data also suggest that these stereotypes are not a tool used by the least informed voters, which is interesting to note. In fact, politically sophisticated voters evaluate leaders most strongly according to the partisan stereotype, although it remains an open question why this occurs.

The subsequent Chapter 6 shifts the attention to the impact of leaders' traits on vote choice and forms the core empirical chapter of the book. Rather than explaining why voters choose parties in particular elections, the author groups parties across countries according to party type (conservative, center-left, and left) and runs separate logit models for these types. Controlling for partisanship and voter ideology, Bittner's results suggest that leader trait evaluations affect vote choice, with evaluations of character having slightly larger effects than those of competence. In other words, positive trait evaluations by voters increase the probability that a voter will vote for the leader's party.

In the final empirical Chapter 7, Bittner looks at the role of institutions and examines whether leader trait evaluations matter more or less in particular electoral contexts. Her results are mixed and no clear pattern emerges, with some institutions having a different impact for leaders of even the same party type. There is some evidence that left leaders' traits have a larger impact in more proportional electoral systems with large party systems. Bittner speculates that this result could be due to the better chances for higher political offices for leaders from small left parties in multiparty systems. She then summarizes the book's findings in a concluding chapter.

Platform or Personality? is a highly engaging study examining three aspects of the literature on party leaders simultaneously: the dimensionality of leader trait evaluations, the factors influencing these evaluations, and the impact of leader evaluations on electoral outcomes. The book builds on existing research, but it does not offer a novel theory of the role of leaders in elections, and does not aim at doing so. Instead, the merit of the book lies in its focused approach of testing existing hypotheses using the most comprehensive and rigorous examination of data on leader trait evaluations to date. The book is also of great interest to electoral researchers more generally, as the research design provides several workarounds to the comparability problem of survey data. Particularly noteworthy are the construction of the leader trait dimensions and the separation of the analysis by three main party types. By conducting the pooled cross-national and longitudinal analysis, Bittner manages to push the available survey data to their limit.

Notwithstanding the impressive data analysis, there are several ways the study could be expanded. First and foremost, the book demonstrates the limits of studying the role of party leaders exclusively with election surveys. Bittner mentions the strategic considerations of parties without exploring them further. But if it is true that leaders' traits have substantial effects on vote choice, then parties are likely to consider them as well. In a multiparty competitive environment, choosing a party leader may not be a trivial task. Examining the constraints inside parties when nominating leaders is therefore crucial to an understanding of the effects of leaders on partisans and voters more generally. For instance, past government or opposition experience is likely to affect parties' leader choices, and consequently the evaluation of leaders' traits by voters, an aspect that is not considered. Moreover, the book could have benefited from a more careful discussion of party platforms, not least because its title raises this expectation. Bittner incorporates the platform only indirectly, by splitting up the analysis according to “party type” and by controlling for the partisanship of voters. Alternatively, a more direct approach would be to control for the ideological proximity of voters to the party position.

In addition, the book discounts the role of political institutions. Early on, an important caveat is raised: Not all party leaders are the same, and the institutional context ought to affect the roles that leaders perform. Despite a final chapter dedicated to the role of institutions, the book does not satisfactorily address the importance of regime type, party system size, and electoral institutions. In a sense, the research design of the book, while enabling a pooled analysis of trait evaluations, comes at the cost of forcing Bittner to discount institutions. Electoral institutions and party systems, however, create particular competitive environments in which parties and leaders run election campaigns. After all, voters cast different kinds of votes in different institutional environments. A vote cast for a party in a parliamentary system with proportional representation does mean something else than one cast for a candidate in a presidential system with single-member districts. Consequently, the way in which leaders and their parties will campaign is also likely to be different. Here, the book could have profited from a theoretical discussion of such effects early on.

Despite these criticisms, Platform or Personality? constitutes a major accomplishment and an important contribution to the literature on the role of party leaders in elections, and the findings should be of interest to electoral and party scholars alike. The book should furthermore stimulate research on the strategic anticipation by parties of the effects of character and competence on voters, on the sources of partisan stereotypes in leader evaluations, and on leader evaluations in complex, multiparty electoral environments.