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One big question has emerged in the wake of Louisiana v. Callais, the Supreme Court’s ruling this week that knocked down the Voting Right Act’s final remaining major pillar: How bad are things about to get? History is a good guide. Our work has shown that the court’s previous assaults on the act have wrought devastating consequences for voters of color. The impact of this decision likely won’t be different. Minority voters will now be left with a diminished voice in American politics, rolling back half a century of steady progress toward racial equality in voting practices.

The Voting Rights Act is one of the most effective laws in American history. Congress passed it in 1965 to ensure that racial minorities, especially Black Americans in the South, could register to vote and cast ballots free from barriers like literacy tests, poll taxes, and other practices that had long suppressed their political participation. The law and its subsequent reauthorizations ultimately made sure that minority citizens’ votes mattered, outlawing policies, such as gerrymandered maps, that watered down their political power.

For decades, the law gave the federal government both a sword and a shield in the battle against voting discrimination. The sword was Section 2 of the law, which allowed the Justice Department or private citizens to go to court when election laws had racially discriminatory effects. The shield came from Sections 4 and 5, which required states, counties, and cities with a history of racial discrimination against voters of color to get permission from the federal government before they could make even the most routine........

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