This is how voter intimidation worked in 1966: White teenagers in Americus, Ga., harassed black citizens in line to vote, and the police refused to intervene. Black plantation workers in Mississippi had to vote in plantation stores, overseen by their bosses. Black voters in Choctaw County, Ala., had to hand their ballots directly to white election officials for inspection.

This is how it works today: In an ostensible hunt for voter fraud, a Tea Party group, True the Vote, descends on a largely minority precinct and combs the registration records for the slightest misspelling or address error. It uses this information to challenge voters at the polls, and though almost every challenge is baseless, the arguments and delays frustrate those in line and reduce turnout.

The thing that’s different from the days of overt discrimination is the phony pretext of combating voter fraud. Voter identity fraud is all but nonexistent, but the assertion that it might exist is used as an excuse to reduce the political rights of minorities, the poor, students, older Americans and other groups that tend to vote Democratic.

In The Times on Monday, Stephanie Saul described how the plan works. True the Vote grew out of a Tea Party group in Texas, the King Street Patriots, with the assistance of Americans for Prosperity, a group founded by the Koch brothers that works to elect conservative Republicans. It has developed its own software to check voter registration lists against driver’s license and property records. Those kinds of database matches are notoriously unreliable because names and addresses are often slightly different in various databases, but the group uses this technique to challenge more voters.