The U.S. Supreme Court’s refusal Thursday to cabin extreme partisan gerrymanders revealed a deep division between Chief Justice John Roberts Jr. and Justice Elena Kagan over the duty of the justices to resolve an issue affecting what one justice has called “the precious right to vote.”

Federal courts have no authority to resolve disputes involving the influence partisanship plays in setting election-map boundaries, a sharply divided high court said in two cases challenging partisanship in redistricting.