It’s a truism of modern politics that Republicans have placed voting rights under assault in the states they control. Ever since the G.O.P. landslides in the midterm elections of 2010, Republicans have worked to restrict the right to vote in a variety of ways—by cutting back on opportunities for early voting, making absentee voting more difficult, and imposing photo-I.D. requirements at the polls, to name only the best known methods. In 2013, in Shelby County v. Holder, the Supreme Court, with a majority of 5–4, gave Republicans the green light to continue their efforts by gutting the Voting Rights Act. The Shelby decision effectively ended the federal government’s supervision of voting rights in states, mostly in the South, that had histories of discriminating against minority voters.