The trick is to keep everything constitutional, Anderson says, staying within the boundaries of the 14th and 15th Amendments, which promised “equal protection” and barred discrimination “on account of race.” As the Virginia politician Carter Glass put it candidly in 1902, “Discrimination! Why, that is precisely what we propose.” It was, he said, an elected official’s duty “to discriminate to the very extremity of permissible action under the limitations of the Federal Constitution, with a view to the elimination of every negro voter who can be gotten rid of, legally.”

Contemporary rhetoric isn’t so frank and incendiary. Anderson describes Georgia’s Exact Match system and the Interstate Crosscheck as modern incarnations of old efforts to restrict the vote. Cloaked in anodyne phrases like “voter roll maintenance,” those database-matching programs “gave the illusion of being clean, clinical, efficient and fair,” Anderson writes, when in fact they had a “horrific effect on voter registration, especially for minorities.” Tiny typographical errors triggered wrongful purges of eligible voters. According to one team of researchers, the Crosscheck program — which was vastly expanded by Kansas Secretary of State Kris Kobach, a staunch Trump ally currently running to be the state’s governor — had an astonishing error rate of 99 percent.

From the perspective of federal enforcement, Anderson says, the situation for minority voters is looking even more perilous now than a couple of years ago. The Department of Justice under Attorney General Jeff Sessions — who as a United States attorney in Alabama tried (and failed) to obtain a conviction of three African-American activists for voter fraud and once called the Voting Rights Act “an intrusive piece of legislation” — has demanded that no fewer than 44 states detail their programs for, yes, voter roll maintenance. The Presidential Advisory Commission on Election Integrity (after reading this book, you won’t be able look at the word “integrity” the same way again) is chaired by two figures who presided over aggressive anti-voter-fraud measures in their home states: Kobach and Vice President Mike Pence.

But at the grass-roots level, Anderson believes that things might be looking up. She offers a surprisingly riveting play-by-play of last year’s special senate election in Alabama, in which Doug Jones, a Democrat, won a startling upset over the Republican Roy Moore. She concedes that Moore, buffeted by allegations of sexual assault, was an especially unappealing candidate, whatever one’s politics. But she also shows how groups like the N.A.A.C.P. mobilized local efforts to help people register to vote and — in a state where poll closures made even getting to the voting booths an issue — to offer crucial transportation.

Behind the tactics deployed by both sides looms a larger question: What kind of future should this country pursue? Should it be a democracy that is, in Anderson’s words, “vibrant, responsive and inclusive”? Or should it be a system that maximizes “the frustration of millions of citizens to minimize their participation in the electoral process”? To that end, this trenchant little book will push you to think not just about the vote count but about who counts, too.