One of the last decade’s most interesting redistricting developments was the adoption of explicit partisan fairness criteria by Michigan and Ohio (sites of two of the 2010s’ most egregious gerrymanders). In Michigan, the new independent commission is required to draw districts that don’t “provide a disproportionate advantage to any political party.” “A disproportionate advantage,” the state constitution continues, “shall be determined using accepted measures of partisan fairness.” In Ohio, if the state legislature enacts a congressional plan by a majority (not a three-fifths supermajority) vote, then the plan must not “unduly favor or disfavor a political party.” For state legislative maps, “the statewide proportion of districts whose voters . . . favor each political party shall correspond closely to the statewide preferences of the voters of Ohio.”
So how have these criteria fared so far? In Michigan, the independent commission decided to consider four measures of partisan fairness (the efficiency gap, deviation from proportional representation, the mean-median difference, and the winning margin difference). The commission also specified that these metrics would be calculated using an aggregate of statewide elections from 2012 to 2020. The commission hasn’t yet finalized its plans but its draft maps, drawn to satisfy this criterion, are dramatically fairer than their predecessors. At the congressional level, for example, the commission’s three draft maps all have efficiency gaps around 1%—compared to an efficiency gap of almost 20% (in a Republican direction) for the 2010s plan.
In Ohio, on the other hand, the Republican-dominated commission flouted the new partisan fairness requirement. Over the last decade, Republican candidates have won an average of 55% of the vote in statewide races. Yet the commission’s state house plan has a Republican seat share of 67%, and its state senate plan has a Republican seat share of 69%. The commission’s required explanation for its plans was also risible. It conceded that, on average, Republican candidates have won just a narrow majority of the statewide vote in recent years. But, the commission continued, “Republican candidates won thirteen out of sixteen of those elections resulting in a statewide proportion of voters favoring statewide Republican candidates of 81% and a statewide proportion of voters favoring Democratic candidates of 19%.” Therefore, “the statewide proportion of districts whose voters favor each political party corresponds closely to the statewide preferences of the voters of Ohio.”
The sleight of hand here is obvious. The commission substituted the proportion of races won by Republican candidates (81%) for the proportion of the vote received by Republican candidates (55%). The latter figure—Republican statewide vote share—represents “the statewide preferences of the voters of Ohio” under both the Ohio Constitution and all accepted methods for assessing partisan fairness. The former figure—Republican candidates’ win rate—is simply irrelevant. Using that flawed statistic, one would have to conclude that the commission’s plans are significantly biased in a Democratic direction. After all, 31% to 33% of the plans’ districts are Democratic—far higher than the 19% of Democratic candidates who prevailed in statewide elections in the 2010s. If Republicans had managed a clean sweep of statewide elections over the last decade, under the commission’s logic, they would be entitled to every single state legislative seat.
What accounts for Michigan’s and Ohio’s very different experiences (to date) with partisan fairness criteria? Most likely, the identity of the line-drawing institution. Michigan’s commission is independent of political actors and balanced among Democratic, Republican, and Independent members. These commissioners have no reason not to faithfully follow all state constitutional requirements. In contrast, Ohio’s commission is composed entirely of politicians and has five Republican and two Democratic members. This Republican supermajority has every incentive to gerrymander (and then to concoct implausible accounts of how its actions actually comply with legal criteria).
The implication for reformers is that, to achieve partisan fairness without judicial involvement, partisan fairness criteria should be paired with structural change—that is, the adoption of a truly independent redistricting commission. As Ohio’s experience demonstrates, partisan fairness criteria alone, unaccompanied by structural change, may easily be ignored by political actors. To be sure, state courts may ultimately insist on compliance with Ohio’s partisan fairness criteria. (Ohio’s new plans immediately prompted a flurry of lawsuits.) But redistricting litigation is costly and time-consuming. Its outcome is also never certain, even given as clear a violation as that presented by Ohio’s facts, due to the issue’s intense politicization. Whenever possible, it seems better to avoid courts and to rely on the structure of the redistricting process itself to prevent gerrymandering.