ON DECEMBER 8th, the Supreme Court heard back to back arguments in cases involving the idea that everyone’s vote should bear roughly equal weight—the so-called “one person, one vote” principle that was developed in a series of cases in the 1960s. Evenwel v Abbott, a challenge to the calculus Texas uses to work out population, makes an appearance in this week’s paper. Harris v Arizona Independent Redistricting Commission, which poses a similarly fraught question about district map-drawing, was argued one hour prior to Evenwel. Harris re-ignites a debate most court watchers thought was long settled: whether and to what extent America's constitution permits partisan considerations to factor into the drawing of electoral maps. Until last week, the justices looked askance only at racial gerrymandering. Now at least a few Supremes seem to be entertaining the idea that there may be sharp limits on partisan political considerations as well, at least where voter equality is at stake. The story of Harris begins with a case with a “Kramer-vs-Kramer”-eque moniker: Arizona State Legislature v Arizona Independent Redistricting Commission. In June, the Supreme Court ruled 5-4 that the federal constitution permits Arizona voters to take redistricting out of the hands of its legislature and, in the hopes of reducing rank partisanship, assign the task to an independent commission. A day later, the Court agreed to hear whether the commission was following through on its promise. The plaintiffs, conservative Arizonans who live in districts they say are unfairly overstuffed, contend that in practice the commission‘s work has been anything but “independent”. “By overpopulating Republican districts,” their brief reads, “the commission unfairly diluted the vote of thousands of Arizona citizens.”

In her majority opinion in last term’s Arizona case, Justice Ruth Bader Ginsburg noted that commissions “have not eliminated the inevitable partisan suspicions associated with political line-drawing”. But, she wrote, “they have succeeded to a great degree” in “limiting the conflict of interest implicit in legislative control over redistricting”. For Justice Antonin Scalia, the cases ought to have reached the Court in reverse order. The sordid truth about the “supposedly divine commission”, he sneered to Paul Smith, the commission’s lawyer, would have been useful knowledge a year ago. “I wish this case had come up before the case we had last term”, Justice Scalia said.

Based on the court’s precedents, though, it is unclear why the facts in Harris should be all that worrisome to the justices. As Mr Smith said, with barely restrained exasperation, “there is simply nothing seriously being argued here that could possibly amount to a constitutional violation”. “There's no problem with this map”, he said. The five commission members (two Republicans, two Democrats and one independent) agreed unanimously on the map and the district court found only a smidgen of partisanship among the motivations of the Democrats. “This is a case where you wonder: Where's the beef? What exactly are we here for?”

A year ago, the justices grappled with an Alabama gerrymander that, some charged, was tinged with racial considerations. Their question was whether the maps in Alabama could be excused as merely political in motivation. Last week, Mr Smith recalled this case to the justices, his voice rising in incredulity:

JUSTICE KENNEDY: Can I put in my notes that you're arguing that partisanship is a valid consideration in redistricting? Is that what you want me to say? MR. SMITH: You ­­certainly can, Your honour. You said it last year in the Alabama case. You said political affiliation is one of the legitimate traditional redistricting criteria that line drawers always can consider.

Mr Smith is right. In the Alabama oral argument, Justice Samuel Alito put the distinction in no uncertain terms: when gerrymandering is based “purely on partisanship rather than on race”, it does not offend the constitution. Fast forward a year, and Justice Alito now seems to think that it is at least arguable that “partisanship is not a legitimate consideration”. This is a puzzling shift.

The development may sound encouraging to those opposed to rigging elections through creative map-drawing, as this paper has been for some time. But several of the justices pointed out in the question-and-answer that scrubbing the redistricting process completely clean of partisan considerations is unrealistic. Stephen Breyer wondered how the court could write a decision that warned map-drafters away from partisanship. “We institutionally can’t review thousands of pages of record in every redistricting case. So what are the words there that describe the standard we should bring to this?” Justice Sonia Sotomayor echoed this concern: “Don't you think this will lead every single plan to be challenged as voter dilution?”, she asked the plaintiffs’ lawyer, Mark Hearne.

In Harris, there is another wrinkle. The commission members chalk up their 8.8% deviation in district-to-district population to the need to comply with a section of the Voting Rights Act that has since been found unconstitutional in the 2013 Shelby County v Holderruling. According to the plaintiffs, this is a red herring. But either way, they say, neither the Voting Rights Act nor partisan considerations justify deviating from the constitutional guarantee of one-person, one-vote.

It is unclear how the justices will resolve Harris. If they throw out the Arizona map, dozens of maps in other states where partisan considerations played a much bigger role in their development may suddenly be called into question. For if partisanship is an illegitimate motivation when distributing a state’s population into districts, it is hard to fathom why it would continue to be acceptable when drawing lines at all. One suspects the justices will hesitate before inviting such an onslaught of new challenges onto their docket.