“It is an invidious, undemocratic, and unconstitutional practice,” Justice John Paul Stevens said of gerrymandering in Vieth v. Jubelirer (2004). Politicians have been manipulating district lines to favor one party over another since the founding of our nation. But with a case starting today, Gill v. Whitford, the Supreme Court may be in a position to crack this historical nut once and for all.

Up until this point, the court didn’t have a standard measure or test of how much one side had unfairly drawn district lines. But “the efficiency gap” could be it. The mathematical formula measures how many votes Democrats and Republicans waste in elections; if either side is way outside the norm, there may be some foul play at hand. According to Loyola law professor Justin Levitt, both the case and the formula arrive at a critical time. “After the census in 2020, all sorts of different bodies will redraw all sorts of different lines and this case will help decide how and where.”