Purcell v. Gonzalez, 549 U.S. 1, 4 (2006)
Purcell v. Gonzalez is the source of the "Purcell principle" — the idea that courts should be cautious about changing election rules in the period close to an election, because late changes risk voter confusion and administrative disruption. It is most often invoked to counsel against judicial intervention shortly before an election. Here, the court cites it for a related point in the opposite direction: the imminence of the upcoming midterm cycle weighs against staying the case, because leaving the rules unsettled would itself create the confusion Purcell warns about. The court pairs it with Justice Kavanaugh's observation that running a statewide election is a "massive coordinated effort" requiring clear and settled rules.