Political gerrymandering, the practice by which a controlling party draws election district lines primarily for the partisan purpose of enhancing its prospects in future elections, has been a subversive force in party politics since the beginning of our republic. It undercuts a foundational principle of our democracy: That we should be governed by those selected by the majority of voters. And, on Oct 3, in Gill v. Whitford, the issue will return to the Supreme Court for the first time in a decade. The justices often have been highly critical of extreme partisan gerrymanders, but the court has yet to identify a judicially discernible and manageable standard for determining when the process by which districts are drawn—an inherently political endeavor—crosses the line and is so partisan as to be unsustainable. For a variety of reasons, there is good reason to believe, and hope, that the court’s disposition in Whitford will change that.

First, the gerrymandering connected to the 2010 redistricting process has caused a historically high level of uncompetitive districts which, in turn, has substantially contributed to the dysfunction and polarization of our democracy. Last year, only 17 out of 435 races were decided by a margin of 5 percent or less, and another 33 seats by a margin of 10 percent or less. Put differently, more than 90 percent of House races were landslides—with an average margin of victory of 37.1 percent—where the results were a foregone conclusion. To be sure, representatives in uncompetitive districts face no real risk of losing a general election. That dynamic creates a strong disincentive to collaborate across the aisle because doing so increases the only serious threat to their incumbency—a primary challenge from the far right or far left. Conversely, it creates an equally strong incentive to move further to the left or right, whatever the case may be, in order to protect their flanks. That is a crucial, but underreported, source of contemporary gridlock and extremism, and it should inform the court’s approach to Whitford. This is not a Democratic or Republican issue. In the past, both parties have been equally guilty of manipulating district lines to gain a political advantage, and there are currently suits by both minority Democrats and minority Republicans challenging redistricting.

Second, the Whitford record, for the first time, offers the court an objective standard for measuring the level of partisanship in legislative maps. In prior cases, several justices have been consistent in their critique of political gerrymanders, calling them incompatible with democratic principles and a manipulation of the electorate. And yet, the court has been unable to agree on a judicially manageable standard for determining when a gerrymander is so partisan as to be unconstitutional. In fact, in Vieth v. Jubelirer (2004), four justices (Scalia, Renquist, O’Connor and Thomas) concluded that, as a consequence of the elusiveness of a workable standard, political gerrymandering claims were nonjusticiable. Four other justices (Stevens, Souter, Breyer and Ginsburg), believed that the claims were justiciable, but they advanced different views of what would be an appropriate standard. Justice Kennedy was the deciding vote in Jubilirer, as he often is, and although he was unwilling to find political gerrymandering claims nonjusticiable, he also was unpersuaded that a manageable standard had yet been identified. Kennedy stated that he could envision a successful challenge, and he signaled his sympathy for the claims with this observation: “[T]hat no such standard has emerged in this case should not be taken to prove that none will emerge in the future. Where important rights are involved, the impossibility of full analytical satisfaction is reason to err on the side of caution.” That is where things stand as the court prepares for Whitford, a case that Justice Ginsburg has intriguingly suggested might be the most important case of the term.

In Whitford, Wisconsin is asking the court to overturn a decision invalidating the 2011 redistricting plan, drafted solely by Republicans, for the lower house of the Wisconsin state Assembly. The new map enabled Republicans to convert very close statewide vote totals into legislative majorities that were not reflective of the popular vote. In 2012, for example, Republicans won 48.6 percent of the statewide vote for Assembly candidates but captured 60 of the Assembly’s 99 seats. In 2014, with only 52 percent of the vote, Republicans won 63 seats.

The redistricting plan was successfully challenged under the First and Fourteenth amendments, marking the first time in more than decades that a map has been struck down as a partisan gerrymander. There was ample evidence to support the trial court’s decision, including emails and documents showing how the Legislature’s consultants used statistics to explain how to draw the maps in a way that would most advantage Republicans. Also in evidence was a string of maps that grew increasingly biased, accompanied by notes from consultants reflecting their understanding of the long-term effects of the maps they chose to use.

What makes Whitford a potential game-changer, however, is that the challengers have supplemented the record with corroborating objective standards that did not exist when Jubilirer was decided. The most interesting of these is called the “efficiency gap,” which measures the degree to which partisanship affects how districts are drawn by tabulating “wasted votes” that result from “packing” and “cracking”—the two main tools of gerrymandering. These refer to packing like-minded voters, such as supporters of the same party, into a limited number of districts, or cracking their influence by scattering them across districts in numbers too small to make an impact. Under the efficiency gap standard, developed by two University of Chicago professors, every voter packed into a district above the threshold needed to elect a candidate from his party creates a “surplus” vote. And someone in a cracked district who votes for a candidate who is unable to win is a “lost” vote. Surplus and lost votes are considered wasted votes. The difference between the two parties’ wasted votes, divided by the total number of votes cast, yields an efficiency gap, and the challengers in Whitford argue that gaps higher than 7 percent violate the Constitution, as they objectively capture the likelihood that the gap would endure over a 10-year redistricting cycle. The gap in Wisconsin was 13.3 percent in 2012 and 9.6 percent in 2014.

The advent of the efficiency gap and other new objective standards injects yet another layer of intrigue to Whitford. In his opinion in Jubilirer, Justice Scalia demeaningly mocked Justice Kennedy for “err[ing] on the side of caution” and refusing to find the claims nonjusticiable on nothing but the hope that a manageable standard might be identified sometime in the future. In a scathing rebuke, Justice Scalia not only questioned the legal underpinnings of Justice Kennedy’s position but went so far as to accuse the justice of not “doing his job.” The identification of a new standard, one that had not been conceived at the time Jubilirer was decided, could effectively vindicate Justice Kennedy’s cautious approach and definitively answer Justice Scalia’s pointed rebuke.

Should the Supreme Court adopt the efficiency gap standard, or one like it, it would be transformative, enabling courts for the first time to adjudicate partisan gerrymandering cases and begin the process of ensuring that truly competitive congressional elections—the bedrock of a healthy democracy—become the norm, and not an aberration. Commentators agree that adoption of a workable standard would strongly discourage obviously partisan gerrymanders for fear of invalidation—which explains why racial gerrymander litigation has subsided since the mid-1990s.

This case undeniably is a political hot potato, probably the most politically significant case since Bush v. Gore. But the insidious redistricting practices employed during the 2010 redistricting cycle, combined with the advent of methodologies to measure the effect of partisanship on redistricting decisions, should give the court the judicial will to come together on a standard. All eyes will be on Justice Kennedy.