For decades, the median voter theorem has provided a useful way to think about party and candidate behavior in US elections. The key to winning elections, according to this theorem, was to appeal to voters in the middle of the ideological spectrum. The party or candidate who did a better job of doing so was on course for victory. In Bases Loaded, Costas Panagopoulos makes a convincing case that such an explanation no longer makes sense for understanding US campaigns and elections. Rather, turnout has become much more important than persuasion in the past 20 years, a development aided by microtargeting, big data, and predictive analytics. Key to winning elections nowadays is mobilizing one’s party base.

Panagopoulos assembles considerable evidence to advance this central claim, much of it from dozens of surveys collected over decades by the American National Election Studies. For instance, data show that the number of persuadable voters has declined over the years, measured both in terms of cross-pressured voters and “swing” voters. A greater percentage of voters know for whom they will vote early during the presidential campaign, and fewer voters are defecting from their party at the ballot box than in the past. Not only have voters changed but so have campaign strategies. Campaigns are now more likely to contact strong partisans than in the past—and are much more likely to contact strong partisans than political independents than previously. These differences are especially pronounced in the post-2000 time period. Panagopoulos also presents data on the use of partisan cues in presidential advertising on television over time. The percentage of ads containing a partisan cue does appear to be higher in recent years, though the percentage does bounce up and down from year to year; thus, Panagopoulos rightly characterizes this finding as “speculative or suggestive” (p. 68). I suspect, however, that had he examined the content of digital advertising, which has exploded in the past decade, he would have found even more support for the idea that messages are increasingly focused on turning out (and raising money from) voters in the parties’ bases as opposed to sending persuasion messages to voters. Given all of the evidence compiled in this book, it is no surprise that turnout among strong partisans has risen over time while falling among political independents: strong partisans make up a greater percentage of the electorate today than they did in the late 1970s and early 1980s.

The shift in campaign strategy, according to Panagopoulos, while happening over decades, reached a more abrupt turning point in the year 2000 when the Bush campaign, led by strategist Karl Rove, focused fewer resources on persuasion and more on turnout. At that same time, new techniques such as microtargeting, which was enabled by the collection of big data on voters and the use of predictive models, allowed for the more accurate identification of persuasion and turnout targets. Another simultaneous development—and this could have been developed more by Panagopoulos in the history of campaigning presented in chapter 2—was the greater willingness of independent groups to use creative interpretations of campaign finance law to organize as 527s, which allowed them to collect unlimited donations and spend unlimited sums on voter mobilization activities.

Why do these changes in campaign strategy matter? According to Panagopoulos, the upshot is that campaigns themselves are at least partially responsible for rising partisan polarization in the United States. Today’s voters, who are more partisan than voters of the past, naturally vote into office more partisan politicians. The difficult question to answer is the relative impact of these changes in campaign strategy on the polarization of, say, the US Congress, versus all of the other drivers of polarization, such as the increasingly fragmented and partisan news media, the rise of the internet, and changes in party nomination procedures and in campaign finance laws, among other factors.

One thing I appreciate is that there is nuance to Panagopoulos’s argument. He acknowledges that campaigns’ pursuit of turnout among strong partisans and persuasion of swing voters is not an either/or proposition; he even unearths a quotation from Karl Rove, the presumed mastermind of Bush’s “all turnout” strategy in 2000, that admits there is room in a campaign for persuasion as well. What Panagopoulos does maintain is that the relative emphasis has shifted away from persuasion and toward turnout, even though campaign contacts with independent and weak partisans have not declined. It is hard to argue against that assertion, given the impressive array of evidence that is presented in this book. Indeed, although the book was written before the 2020 presidential election in the United States, the conduct of the Trump campaign—which made very few concessions to middle-of-the-road voters and sought to gin up base turnout through racial dog whistles and false claims—seems to lend even more support to Panagopoulos’s thesis.

If there is a weakness in the book, it is that the central argument is defended solely at the level of presidential campaigns. My impression is that campaigns for lower-level offices, especially the US House and Senate, may be following the presidential campaigns in stressing turnout over persuasion, though perhaps not to the same degree. For one, many of these campaigns do not have the endless resources of a presidential campaign that would enable them to model the entire voter file, thereby enabling fine-grained microtargeting. Obviously, however, this is an empirical question, and I would love to have seen some evidence speaking to the patterns of voter contacts—and turnout by partisanship—in midterm congressional races. Admittedly, some of the data necessary to provide these analyses may not be available going back several decades in time. I also wonder to what extent the argument applies to statewide races. There still had to be considerable campaign persuasion in Massachusetts and Maryland, two very Democratic states that elected Republican governors in 2018, and in Kansas and Louisiana, two very Republican states that elected Democratic governors in 2018. I would be curious to hear Panagopoulos speculate on why these cases are seeming departures from his argument, and whether we can expect fewer such anomalies in the future and under what conditions.

Bases Loaded is a trim book, but that is not a criticism. There are few wasted words. The analyses are, by and large, straightforward enough that a clever undergraduate student could understand them. There are also dozens of visual displays of data that help the reader sift through the evidence. Ultimately, Panagopoulos successfully makes the case that presidential campaigns have shifted from an emphasis on persuading the median voter to convincing their partisan supporters to turn out on Election Day. Yet he does not insist that this trend will continue indefinitely. He writes, “The patterns detected in this book are likely tentative and subject to change and fluctuation as parties and campaigns continue to adapt to ever-changing sociopolitical and contextual circumstances” (p. 110). The question then becomes, What circumstances could lead campaigns to return to a focus on persuasion? The irony, it seems, is that a less polarized electorate—something that current base-mobilizing campaign strategies are working in opposition to—is almost a precondition for a return to persuasion-focused campaigns.