Political Geographers’ Amicus On Distinguishing Partisan Gerrymandering From Natural Geographic Clustering

I want to single out, in two posts, two amicus briefs in Whitford.  I am co-counsel on the first, filed on behalf of a group of academic experts in political geography (see here).

I chose to represent these experts because I considered it particularly important that the Court be aware of the social-scientific techniques that now exist, and that are being further developed, that enable courts to determine objectively whether the partisan advantages in a districting plan are the result of intentional partisan gerrymandering or of “neutral factors,” such as the greater natural geographic clustering of one party’s voters (typically, Democrats in cities). Many of the other briefs in the case, from both the challengers and the State, as well as from other amici, refer to the work described in this brief, which is being done by academics such as Jonathan Rodden, Jowei Chen, Wesley Pegden, Wendy Tam, and others.   This brief provides a full explanation of these techniques, which are now available and can help provide a judicially manageable standard for adjudicating partisan gerrymandering claims.

In determining whether partisan gerrymandering has occurred and to what extent, other social scientists have developed means of analyzing whether districting plans treat the two major parties in symmetric fashion:  if Democrats win 55% of the vote but gain 65% of the seats, that is not necessarily a problem of partisan gerrymandering if Republicans would also gain 65% of the seats if they won 55% of the vote.  But while being able to determine whether a plan treats voters of each party the same or “asymmetrically” is an important first step, it is still just that.  For it remains possible that this difference in how the two parties fare might be the result, as noted above for example, of the natural geographic clustering of one party’s voters.   Indeed, the Appellants and the Wisconsin legislature both defend Wisconsin’s plan party on this basis.

The techniques described in this brief enable the next step of analysis:  distinguishing between plans that favor one party, but for legitimate or neutral reasons, and those that can best be explained as doing so only as a result of intentional partisan gerrymandering.  At the time of the Court’s last major confrontation with the issue of partisan gerrymandering in the Vieth case (2004), Justice Kennedy withheld judgment but recognized that “new technologies may “produce new methods of analysis that make more evident the precise nature of the burdens gerrymanders impose,” which would “facilitate court efforts to identify and remedy th[ose] burdens.”  This brief describes precisely these important new methods of analysis that have emerged since Vieth.

The political geographers’ amicus brief describes three related techniques.  I won’t try to re-create all of that discussion here.  But the first technique, which has become the most widely known and has been judicially endorsed, by the Fourth Circuit in this opinion, takes advantage of modern computing power to create vast numbers of simulated districting plans based on traditional districting criteria, which can then be compared to the enacted plan.  As the Fourth Circuit put it, the logic of this technique is that “if a computer randomly draws five hundred redistricting plans following traditional redistricting criteria, and the actual enacted plans fall completely outside the range of what the computer has drawn, one can conclude that the traditional criteria do not explain that enacted plan.”

In the Wisconsin case, each of these three analytical methods for measuring the effect of political geography support the conclusion that the Wisconsin plan is an extreme, intentional partisan gerrymander.  That is particularly noteworthy, because two of the signatories to the brief — Professors Rodden and Chen — had concluded in an important article applying the simulated-plans technique that part of the Republican advantage in the House was best explained not by partisan gerrymandering, but by the greater natural geographic clustering of Democratic voters.  Yet applying that same technique here, they conclude the Wisconsin plan cannot be explained by “clustering” but only by intentional partisan gerrymandering.


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