SINCE AT LEAST 2004, when the Supreme Court rejected a challenge to Pennsylvania's congressional district boundaries because there was not a good enough way to quantify gerrymandering, the problem facing would-be reformers is this: How do you measure something that's best understood by how it affects other things?
Last year, reformers thought they had solved that conundrum. Armed with a new metric called the "Efficiency Gap"--a formula that claims to demonstrate how gerrymandering makes congressional races less competitive--they asked the Supreme Court to toss out Wisconsin's congressional map.
The court refused, emphatically. In a unanimous ruling, the nine justices agreed that the Supreme Court would not be responsible "for vindicating generalized partisan preferences." The court could, however, be interested in adjudicating specific cases of disenfranchisement as a result of unfairly drawn districts, Chief Justice John Roberts wrote at the time.
Enter Faulkner Fox, a plaintiff in League of Women Voters v. Rucho, a new gerrymandering case that will go before the Supreme Court this spring. Fox is a progressive activist from Durham, North Carolina, who says that state's unfair congressional districts have made her work "almost irrelevant."
In some ways, she's right. Despite being a purple state, Republicans have held 10 of North Carolina's 13 congressional seats since a GOP-controlled redistricting prior to the 2012 election. But again, that merely describes an effect of gerrymandering and not the thing itself.
By arguing that specific plaintiffs, like Fox, have had...