The 2-1 federal court decision striking down Wisconsin’s redistricting plans for the state legislature as an unconstitutional partisan gerrymander, Whitford v. Gil, is without doubt the most significant lower federal court decision on partisan gerrymandering the lower courts have ever issued. The case will also come to the Court in the Supreme Court’s mandatory, appellate jurisdiction — which now exists only for a tiny sliver of cases, including challenges to statewide redistricting plans.

The normal route through which cases come to the Court is via petitions for certiorari. In those cases, the Court has complete discretion to decide whether to hear a particular case. But for cases in the mandatory appellate jurisdiction, the Court has only two options: summarily affirm the decision below or hear the case. One of the policy aims Congress had in mind in deploying mandatory jurisdiction for federal challenges to statewide redistricting plans was to get these cases resolved more quickly, given the time sensitivity of these kind of cases. But that policy objective conflicts with other policy concerns about the timing of Supreme Court review, and the WI case brings to the surface these conflicts.

In striking down a statewide redistricting plan as an unconstitutional partisan gerrymander, the WI decision is the first of its kind. In addition, the court relies in some part on a new statistical measure, the Efficiency Gap (EG), which is designed to help determine the extent of partisan gerrymandering in election maps. I do not want to overstate the extent to which the court relies on the Efficiency Gap; the court essentially uses the EG to corroborate the findings on partisan intent and effect it has otherwise reached. But in terms of both doctrinal development and methodology, the decision does break new ground.

If this case were coming to the Court in its certiorari jurisdiction, the Court would be able to decide whether to postpone review until other federal courts had had an opportunity to respond to the WI decision. If lower courts accepted the general approach of the WI court, what would this mean about how narrowly or expansively a partisan gerrymandering doctrine with teeth would be in application? As lower courts grappled with arguments about the EG in the specific contexts of different districting plans, what conclusions would they come to about the relevance and usefulness of this measure? In the language of Supreme Court practice, the Court could bypass review in the WI case, the first of its kind, and wait for the issues to “percolate” in the lower courts. The Court would then have a richer reservoir of judicial experience on which to draw in deciding the appropriate doctrinal response.

With mandatory appellate jurisdiction, the Court loses the ability to consider any of these factors. The Court either has to summarily affirm (a high threshold to get over for lower court decisions involving novel doctrinal and methodological developments in important areas) or jump in on the merits the first time a three-judge federal court breaks new ground in a case that falls, as the WI case does, within the Court’s mandatory appellate jurisdiction.