Why does aggregate partisanship change over time? Why does it remain stable? Why do population subgroups change their partisanship or maintain stable partisanship over time? These are central questions of interest to scholars and popular observers alike. They are particularly timely in an era in which the rise of populist and authoritarian figures has presented a challenge to long-standing parties and restructured partisan loyalties in the process.

In this imaginative book, Ken Kollman and John E. Jackson address these questions in examinations of four polities: the United States, the United Kingdom, Australia, and Canada. The authors present a unified framework for examining the dynamics of partisanship in multiple electoral contexts. As they note (p. 50), five features distinguish their approach: (1) it can accommodate a variety of partisan dynamics from stasis to fluctuations in partisanship to both rapid and slowly evolving realignments (what the realignment literature calls critical and secular realignments); (2) the macro model of partisanship is based on a micro-level model that is both theoretically and empirically defensible; (3) different temporal units can be examined, from quarterly to biennial data; (4) the model can be applied to a variety of party systems, from two-party systems to 2.5-party systems to multiparty systems; and (5) the behavior of political parties plays a principal role in producing the dynamics of partisanship.

Let’s examine this last feature of the book’s analysis first. Kollman and Jackson (p. 16) posit three alternative processes that could produce partisan dynamics. The first is that people change, that voters’ preferences change and this leads to changes in levels of support for parties over time. The second is that circumstances change, that voters evaluate the performance of the incumbent party in a form of retrospective voting and update their partisan preferences accordingly. The third is that the parties change, that they change their positions on issues and that this leads voters to update their preferences in response. Kollman and Jackson (p. 17) conclude that while all three processes are no doubt in play in elections, the third process plays the largest role, with the first playing a secondary role, and the third playing the least role. In short, the behaviors of parties are the greatest contributors to changing partisanship.

The insights of the book are numerous, far too many to document in a short book review. Among the detailed implications of their models is that the effect of economic factors on partisan dynamics varies across the countries examined. In the United States and Australia, for example, economic performance has only short-term effects on normal partisanship. In contrast, in the United Kingdom, economic performance becomes a component of voters’ utilities for the parties and thus plays a critical role in shaping long-lasting normal partisanship. In Canada, voters are much more likely to reconsider their partisanship in each election, to the point that short-term factors shape partisanship and “it is not possible for a normal partisanship to develop and to become an integral part of people’s belief systems” (p. 159).

One of the particularly attractive features of this book is the attention to the connection between the micro- and the macro-levels of partisanship. Because the macro model is predicated on a rich micro-level model, the authors are also able to examine partisan dynamics for distinct subgroups, such as Southern Black voters and Southern White voters in the United States. In a chapter with Elizabeth Mann Levesque, the authors find that Southern Black voters’ dynamics are consistent with what realignment scholars would term a critical election, in 1964, while Southern White voters’ dynamics are reflective of scholars would term a secular realignment extending over multiple decades. Changes in the parties’ positions on issues played central roles in producing both groups’ partisan dynamics.

The book examines the dynamics of several other groups’ partisanship as well. These include working- and middle-class voters in the United Kingdom, voters in the western provinces and Quebec in Canada, and Protestant and Catholic voters in Canada. The book also examines how different party systems fit the four countries examined. Perhaps unsurprisingly, a two-party system fits the United States best, while the United Kingdom’s party system is reflective of a 2.5-party system, Canada’s reflects a multiparty system, and there is evidence consistent with either a two- or 2.5-party system in Australia (p. 166).

One subject readers might like to see discussed more is populist and authoritarian figures and movements’ effects on partisan dynamics. In what ways has the rise of such figures and movements that challenge the status quo of established party systems affected the dynamics of partisanship in recent years? What does the future hold for partisan dynamics as a consequence of such developments? There is some discussion of former President Trump in the context of the 2020 election in the final chapter, but the reader is left wanting to see a fuller development of this topic. This subject could make for an interesting extension to the book by the authors or by scholars seeking to apply Kollman and Jackson’s modeling approach to these dynamics.

Similarly, scholars might be interested in applying Kollman and Jackson’s model to developing party systems. What are the dynamics of partisanship in emergent party systems following democratization? Here, modifications of their modeling approach created for studying more developed party systems to the study of cases of emerging party systems could help us better understand the dynamics of both types of systems.

There is much to recommend in Kollman and Jackson’s book. The firm grounding of the dynamics of aggregate partisanship in micro-level models, and the application of these across multiple polities and, by extension, to multiple population subgroups in these polities is one of this book’s principal contributions. Another critical contribution is the finding that party strategies play a central role in producing partisan dynamics. Parties play a substantial role in changing the partisan dynamics of voters in their countries through the positions they adopt. Importantly, this effect varies by country. For example, the key role that economic performance plays in the United Kingdom makes normal partisanship in this country quite distinct from normal partisanship in the United States and Australia and, by extension, could be seen to temper elites’ agency in shaping normal partisanship in the former country as opposed to the latter two. The dominant role of short-term forces in Canada, in contrast, gives parties considerably more leeway in shaping partisanship de novo at each election than is the case in the other countries, where normal partisanship has a greater effect on aggregate partisan dynamics.

In conclusion, scholars and popular observers interested in partisan dynamics will find much of interest in Kollman and Jackson’s work. The book and its integrated model are likely to have considerable influence on the study of partisan dynamics not only across the countries examined in the book but other countries as well in the years ahead.