The authors of this book make a strong and timely empirical claim that the effects of partisan gerrymandering were dramatically exacerbated during the most recent round of redistricting, effects that cannot be explained by nonpolitical factors. Further, they argue that the Supreme Court played a critical role in this development, and thus the Court also has a responsibility to address it. Specifically, the Court’s 2004 decision in Vieth v. Jubilirer unchained legislatures from hypothetical constraints, constraints that should be reestablished through a more sophisticated and nuanced version of a partisan symmetry test. Gerrymandering in America is a valuable contribution to both the legal debate on the constitutionality of partisan gerrymanders and the empirical debate over their effectiveness. Although I find the claims by Anthony McCann and his colleagues about the centrality of Vieth somewhat incomplete, their quantitative work represents a significant step forward in understanding how partisan gerrymanders actually work.
The book begins with a legal history of gerrymandering in the Supreme Court, with the relevant cases appropriately highlighted and encapsulated. This section also nicely explores some of the less obvious implications of cases that may seem merely adjacent to partisan gerrymandering, such as those dealing with population equality. These cases tie into a theme running throughout the book that partisan gerrymandering violates a fundamental “federalist” principle that the House of Representatives should be elected directly by the people and not controlled by state governments.
The heart of the book makes the argument that partisan bias in the current redistricting cycle a) is significantly larger than in past cycles, b) cannot be entirely explained by demographics or geography, and c) can be explained by partisan political motivations. The authors first lay out a strong empirical case that gerrymandering in the 2010s has been more biased than at any period in the recent past. They do this by means of a chapter exploring the measure of partisan symmetry that becomes the crux of both their analysis and legal prescription. Importantly, their measure takes seriously the notion that statewide votes both vary significantly from election to election and are not always most appropriately analyzed at the 50/50 point, where the vote is equal for both parties. The authors here provide helpful and illuminating graphs of various types of gerrymanders, employing examples from simplified toy states, real states in 2012, and the nation as a whole. The presentation in this chapter is excellent, giving readers a strong intuitive sense of both the partisan bias measure and how it is reflected in many different types of maps.
Before considering political motivations, the authors address the geographic explanation that Democrats are inefficiently clustered in compact urban areas, leading to a natural Republican bias in maps. They divide this claim into a “strong” version—that geography forces states to adopt biased plans—and a “weak” version—that geography merely contributes to bias. Refuting the “strong” version merely requires showing that an unbiased map is possible, for which the authors rely mostly on examples in several swing states from Micah Altman and Michael McDonald. More originally, they address the “weak” version by showing that Republican bias strongly increased in the past decade in many states with Republican maps despite a decrease in the Democratic skewness in the population. In contrast to the conventional wisdom that has developed surrounding this argument, their analysis suggests a surprising asymmetric effect of geography, that “while the urban concentration of Democratic voters makes producing districting plans biased toward Republicans only slightly easier, it makes producing pro-Democratic gerrymanders very hard” (p. 117). This chapter concludes with an intriguing comparison to the United Kingdom, where the nonpartisan boundary commission’s lines have often led to biased outcomes favoring Labour.
The argument that political motivations were responsible for increasing bias also proceeds in two steps. First, the authors show that Republican bias in the 2010 cycle has been most prevalent in states that had both the motive to gerrymander (a competitive electoral environment) and the opportunity to do so (through unified statewide control). The notion that the motive for gerrymandering is only present when the state is nationally competitive is somewhat perplexing both in theory and practice. The authors do not sufficiently justify why such a motive would be absent in a noncompetitive state, especially when the less competitive party controls the process, as in Arkansas. Additionally, they apparently code such states as Alabama and West Virginia as “competitive” but Minnesota and Colorado as “noncompetitive” for unexplained reasons. But more essential to their conclusion, they demonstrate that even in states where this motive and opportunity existed for Republicans in both decades, bias increased significantly in several states between the 2000s and 2010s.
The book concludes with a detailed discussion of the Vieth decision, which the authors call an “unnoticed” revolution, and an argument, largely drawn from social choice theory, that the constitution should demand partisan symmetry, with symmetry measured over each party’s winning a range from 45% to 55% of the vote. The authors’ incorporation of a bias standard across a range of statewide election results is commendable and gives a much more realistic picture of the likely range of outcomes in competitive states. But it is again implicitly dismissive of the idea that noncompetitive states could be gerrymandered as well. Why should we so limit the scope of analysis in states like Massachusetts or Oklahoma, where one party may win 65% of the statewide vote and every seat? Maps in these states may look unbiased at the 50/50 or 55/45 point (as the authors observe), but may nevertheless be drawn to the benefit of one party under their typical noncompetitive circumstances.
In their chapter on political explanations, the authors find that noncompetitive states tend to show less bias even when the opportunity to gerrymander exists, but this may be simply because they are measuring “bias” in the wrong range. They acknowledge this possibility, where “Democrats in Massachusetts have long separated Boston into several districts that also take in some rural areas. This serves to ‘homogenize’ the state politically” (p. 150). Their graphical depictions of bias also include a range of extreme election outcomes, and show examples where these extremes may represent a typical vote. Yet their proposed legal standard would not flag any such partisan gerrymanders.
There is also a brief discussion of midterm turnout to explain why so many swing states may have had Republican majorities during the 2010 redistricting process. This section seems unnecessary and out of place in a book on districting. And historically, midterm elections have been consistently more anti-incumbent party than pro-Republican (e.g., the Democratic wave as recent as 2006). The pattern in redistricting control can be straightforwardly explained by the large Republican wave election in 2010, combined with the targeting of state legislative seats in that year.
Finally, although the authors systematically show that partisan gerrymandering strengthened in the decade subsequent to Vieth, they need to do more to establish a convincing causal link. They claim that the conservative plurality that came close to holding partisan gerrymandering claims nonjusticiable freed legislatures from hypothetical constraints placed on them by unclear prior Court precedent. Although the Court has never struck down a partisan map, prior to Vieth the possibility existed that they might, and Vieth all but removed this possibility. But there are other explanations. Polarization, addressed here in a somewhat perfunctory manner, may increase both the incentive to gerrymander and the likelihood in which state legislators would agree with egregious partisan gerrymanders. And the controversial mid-decade redistricting in Texas occurred prior to the Vieth decision. Could not the fact that this event was accepted by the Court and ultimately acquiesced to by the public have been what emboldened subsequent legislators at least as much as Vieth? Really demonstrating that Vieth specifically caused more effective partisan gerrymanders demands a bit of qualitative analysis, along the lines of the recently published Rat****ed by David Daley (2016), which highlights an unprecedented partisan effort in 2010 by the Republican Party to target state legislative seats in swing states.
Thus, both the casual argument and proposed solution presented in Gerrymandering in America strike me as incomplete. Nevertheless, its authors make an innovative and cogent case that partisan gerrymandering is more urgent and problematic than ever, and very effectively revive and develop the partisan symmetry standard to make this case. Despite not presenting the definitive solution, the book is an important addition to this highly salient debate.
