If insanity is doing the same thing over and over and expecting a different result, then litigants who challenge gerrymandering must be mad. Last month, a federal court threw out the Texas Democratic Party’s claim that the state’s new congressional and state house districts are unlawful. This was the twelfth time in a row that this sort of claim has failed in the current cycle. Plaintiffs’ record of futility now spans at least three dozen cases over four decades.

It doesn’t have to be this way. Litigants keep losing these lawsuits because they keep proposing standards the courts have already rejected (such as partisan intent). They’re failing to capitalize on encouraging comments by the Supreme Court, which show that it’s open to a test based on partisan symmetry—the idea that district plans should treat the parties equally. In a forthcoming law review article, Eric McGhee and I lay out just such a test. If plaintiffs were to use it in litigation, they’d have a fighting chance at winning. And if they were to win, then the whole landscape of redistricting in America would be transformed.

First, some background. States redraw their districts every ten years in order to equalize their populations. When this redrawing occurs, the party in power often tries to disadvantage (or gerrymander against) the opposing party. Gerrymandering takes the form of packing the opposition’s supporters into a handful of districts (where they win in landslides) or cracking them among multiple districts (where they lose by slim margins).

Gerrymandering is an age-old practice, but in a 1986 case, the Supreme Court held that it can be unconstitutional if it’s severe enough. The Court confirmed this holding in a pair of decisions in 2004 and 2006. But these cases rejected just about every proposal for identifying unlawful plans. “Predominant partisan intent,” “disregard for traditional districting criteria,” “minority party entrenchment”—none of these were workable standards, in the Court’s view. But these are precisely the standards that plaintiffs have continued to suggest.

While the tone of the 2004 and 2006 decisions was mostly dour, there were glimmers of hope in the latter case. Justice Stevens wrote excitedly about the concept of partisan symmetry: the idea that “the electoral system [should] treat similarly-situated parties equally” in terms of the conversion of votes to seats. Symmetry isn’t the same as proportionality (long the Court’s bête noire), because it asks only that the parties’ votes translate into seats with equal efficiency, not that their shares of votes and seats be identical. Justice Souter commented that “[i]nterest in exploring this notion [of symmetry] is evident.” And the Court’s enigmatic swing voter, Justice Kennedy, added that he was not “discounting its utility in redistricting planning and litigation.”