What is the test for a state to justify an infringement on established voting rights?

In order to justify an infringement on established voting rights, the state must satisfy strict equal protection standards and show that the distinctions drawn are necessary to further its purpose and that the restraints on the franchise are justified by a compelling state interest. (Curtis v. Board of Supervisors (1972) 7 Cal.3d 942, 952, 104 Cal.Rptr. 297, 501 P.2d 537; Williams v. Rhodes (1968) 393 U.S. 23, 31, 89 S.Ct. 5, 10, 21 L.Ed.2d 24.)