In a case that could eventually affect the balance of legislatures across the country, a federal court in Wisconsin has for the first time struck down a partisan gerrymander. The U.S. Supreme Court has previously declined to regulate such party-based districting, but this time may well be different. The lower court gave a simple, clear rule for determining whether districting is designed to disadvantage one party systematically. And the growing disparity between Republican and Democratic-controlled state legislatures gives the justices — especially Anthony Kennedy — very good reason to intervene.
The facts of the case are being repeated all over the country. The Wisconsin state legislature, which sets state and federal electoral districts, is Republican controlled. After the 2010 census, it introduced a new districting plan that was designed by experts with computer programs so sophisticated that they make the task simple. The plan was to increase the number of Republicans elected using techniques called “cracking” and “packing.”
Cracking means taking voters from the disfavored party — here, Democrats — and spreading them out across districts so they will have less than a majority. The votes of the losers are then systematically wasted.
Packing means that in some districts, the party in power puts large numbers of the other party into districts that they will win. This, too, wastes votes, because every vote beyond 50 percent plus one is unnecessary to win the district.
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Formally, cracking and packing don’t violate the principle of one person, one vote, because the districts can all be the same size. It would be blatantly unconstitutional to use these techniques to disenfranchise voters because of their race, but no court has previously said the techniques are unlawful when applied to disenfranchise members of a political party.
In Wisconsin, the gerrymandering worked. In 2012, Republicans won 48.6 percent of the statewide vote and got 60 of the 100 seats in the state assembly. In 2014, they got 52 percent of the vote and won 63 assembly seats.
The special three-member district court on Monday struck down the use of the techniques as violating the equal protection clause of the Constitution. To get there, it had to overcome a serious legal hurdle: the lack of a direct Supreme Court precedent prohibiting partisan gerrymanders.
On several occasions, most notably in the 1986 case Davis v. Bandemer, the court has entertained the possibility that “at least in some cases — the intentional drawing of district boundaries for partisan ends and for no other reason violates the Equal Protection Clause.”
But the court hasn’t been able to come up with an easily applied test to distinguish illegal, systematic gerrymandering from garden variety gerrymandering that inevitably has some political motivation.
The court in the Wisconsin case claimed to have found a solution, dreamed up by two law professors, Nicholas Stephanopoulos and Eric McGhee. It’s known as the efficiency gap, and it’s impressively simple.
To measure the efficiency gap, you first tally up the votes wasted by each side. For the winners in a district, that’s the total votes beyond what was needed for victory. For the losing side in a district, it’s all the votes cast. Then, for each party, you divide the wasted votes by the total number of votes cast. That yields a rough measure of vote efficiency for each party.
What you find is that the party that has been cracked and packed has a much lower efficiency than the party that hasn’t. On that basis, the court struck down the partisan gerrymander.
The Supreme Court will now have to decide whether to accept the efficiency gap measure. In practice, that means it will be up to Kennedy, who will remain the swing vote even when a replacement for Scalia has been named.
In the 2004 Vieth case, Kennedy was on the fence. He wrote a concurrence that said he didn’t want to eliminate the possibility of partisan gerrymandering claims, but he wasn’t convinced a measure could be found.
And Kennedy offered his own, creative theory that partisan gerrymandering might violate not equal protection but rather free association. His idea was that everyone gets an equal vote, but those who associate with one political party face discrimination by the state through dilution.
Kennedy might well buy the efficiency gap analysis. And he has extra reason to do so now.
Almost three-quarters of state legislatures are in Republican hands, which demonstrates how dangerous partisan gerrymandering is to the continued viability of two-party democracy. Partisan gerrymandering entrenches small advantages and makes them big. Because state legislatures set federal congressional districts, this is a part of the reason the U.S. House is so heavily Republican.
With the political branches of government in Republican hands, any reform must come from the courts. The Wisconsin case may become the most important judicial decision of our political era.
Noah Feldman, a Bloomberg View columnist, is a professor of constitutional and international law at Harvard.