IN his opinion for the majority in the Supreme Court’s 2013 Shelby County decision, which struck down a major section of the Voting Rights Act, Chief Justice John G. Roberts Jr. wrote that “history did not end in 1965.” But the sad truth is that voter-suppression efforts did not end, either.

In 2014, the first post-Shelby election, thousands were turned away by new restrictions in states like Texas and North Carolina. A 2014 study by the Government Accountability Office found that voter ID laws in Kansas and Tennessee reduced turnout by 2 to 3 percent during the 2012 election, enough to swing a close vote, with the highest drop-off among young, black and newly registered voters.

This could be a disturbing preview for 2016, which will be the first presidential contest in 50 years where voters cannot rely on the full protections of the act. New restrictions will be in place in up to 15 states, which account for as many as 162 electoral votes, including crucial swing states like Ohio, Wisconsin and Virginia.

The act, signed 50 years ago today, was the crowning achievement of the civil rights movement. It swept aside longstanding practices that disenfranchised voters, and prevented new ones from emerging: Between 1965 and 2013 the Justice Department and federal courts blocked more than 3,000 discriminatory voting changes. But it is precisely that capacity, known as preclearance, that the Roberts court invalidated.