That labyrinth has been under construction for years. Kemp has embarked on what his opponents and critics say is a series of naked attempts to constrict the electorate. Since 2010, his office reports that it has purged upwards of 1.4 million voters from the rolls, including more than 660,000 Georgians in 2017 and almost 90,000 this year. Many of those voters found their registration canceled because they had not voted in the previous election. Additionally, under an “exact match” law passed by the state legislature that requires handwritten voter registrations to be identical to personal documents, 53,000 people had their registrations moved to “pending” status because of typos or other errors before a district court enjoined the policy. More than 80 percent of those registrations belonged to black voters.

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Most of these maneuvers have rather small effects in a vacuum, and it’s difficult to track the effects of any one policy on the outcomes of elections. For example, Georgia’s early-voting period featured a record-shattering 2 million votes cast, a number that dwarfs the thousands of people who could have faced disenfranchisement under the exact-match law. But much of the research on election law and voter turnout shows that it’s the combination of major policies and minor barriers—like polling-place changes, long lines at the polls, and small bureaucratic hurdles—that have real and measurable impacts on turnout.

According to a new working paper from the Harvard University professor Desmond Ang, protections against those accumulative assaults against democracy have all but been erased in the past five years. Ang studied the effects of a provision in the Voting Rights Act (VRA) that required the federal preclearance of election laws in places where Jim Crow had kept black people from voting, a requirement that was expanded in 1975 to some states and districts outside the Deep South. As originally envisioned, preclearance forced districts with significant proportions of minority voters and low minority turnout to submit all changes to election laws for federal approval. The federal litmus test approved new provisions only if they were found not to decrease minority turnout relative to the status quo. Thus, the VRA was not only a protective shield against scorched-earth Jim Crow policies—it was also intended to guard against more subtle restrictions, all while promoting higher minority turnout as an explicit goal.

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Ang found that in the districts covered by preclearance from 1975 to 2013, federal oversight was a major factor in sustained increases in minority turnout relative to counties not covered by the VRA. And that doesn’t include counties and states that had more explicit anti-black laws, like poll taxes, that the VRA outlawed. Ang’s findings indicate that the act of continued federal monitoring alone was responsible for a good deal of minority turnout across the country. “The estimated gains in voter turnout are large—ranging from 4 to 8 percentage points—and lasting—having persisted for 40 years,” Ang writes.