Every decade, when state legislatures across the country draw districts for themselves and their congressional delegations, some lawmakers violate voters’ constitutional rights by packing members of the minority party into as few districts as possible. At least, that’s what the Supreme Court has hinted at in past rulings, when it wrote that extreme partisan gerrymandering can violate voters’ First and Fourteenth Amendment rights to freedom of speech and due process. The problem, the Court wrote in its 2006 League of United Latin American Citizens v. Perry decision, is that it can’t strike down gerrymandered maps without some sort of tool to determine exactly when district boundaries are skewed so drastically that they discriminate based on voters’ party affiliations. The winding, snake-like districts often used to illustrate gerrymandering aren’t necessarily signs of ill intent, and it’s often necessary to have some variation in how polarized or competitive districts are. But the Wisconsin-based plaintiffs in a lawsuit filed this summer think that they have found the formula that the Court has been waiting for. And if they manage to push their case to the high court and win, the lawsuit’s consequences could extend from Wisconsin across the entire nation.
In a new U.S. District Court case, Whitford v. Nichol, the plaintiffs propose judging gerrymandering via a concept called the “efficiency gap,” based on an academic paper written in 2014 by political scientists Nicholas Stephanopoulos and Eric McGhee. The proposal is surprisingly simple for such an arcane subject: Start by adding up each party’s “wasted” votes that don’t help them win a district. (If Party A wins 90 votes out of 100, 39 of its votes are wasted, since it only needs 51 for a majority. All 10 of Party B’s votes are also wasted in this scenario.) The difference between each party’s wasted votes, divided by the total number of votes cast, is the “efficiency gap.”
Across the Wisconsin State Assembly, Stephanopoulos and McGhee found a 13-percent efficiency gap in 2012 and 10-percent gap in 2014, both favoring Republicans. That translates to Republicans winning 13 percent more seats in 2012 and 10 percent more in 2014 than they would have under a map that treated members of both parties equally.
In Whitford, the plaintiffs use the efficiency gap to illustrate how steeply disadvantaged Democrats are in the state. But because Whitford is the first time that any plaintiffs have proposed this kind of test to measure the extremity of gerrymandering, the lawsuit’s repercussions could extend far beyond Wisconsin.