The mostly conservative narrative about election fraud is pervasive, though unfounded: voter fraud is at nearly zero percent in the United States. But it’s not exactly surprising that Trump’s increasing and alleged concern for electoral fairness comes at the precise moment that polling shows his support to be decreasing in several key states and his campaign finds itself in a tailspin. In fact, the two may be closely (and inversely) related: If the race doesn’t look like it’s going in the right direction, contest the results—a strategy adopted by spoilsports and despots alike.

Trump has thus far offered no evidence for his new concern beyond “you’ve been reading the same stories I’ve been reading,” (perhaps these stories include a debunked research paper on the Democratic primary) but he has nonetheless urged his supporters forward. On Trump’s website, those heeding the call can now sign up to be a “Trump Election Observer” with the explicit goal of helping the candidate “Stop Crooked Hillary From Rigging This Election!” (Never mind that the party trying hardest to tamper with American politics is Russia, not Rodham—and that thus far the Republican has been the beneficiary of said manipulations).

What, practically, does Trump mean? It’s not as if his supporters can follow unsuspecting voters into the booth, or conduct cyber-monitoring or check the hanging chads—but U.S. election law is remarkably permissive when it comes to so-called “election challengers.”

According to a study by the Brennan Center, 39 states currently permit private citizens—including, say, Trump supporters or Clinton supporters—to challenge prospective voters on Election Day. What happens to the voter varies, explained Wendy Weiser, director of the Brennan Center’s Democracy Program.

In some states, those challenging must provide election officials with some sort of valid reason for contesting a voter’s eligibility.

But in 24 states, private citizens can challenge a voter at the polls without offering any documentation that might call this eligibility into question.

All this means that a challenger intent on, for example, “stopping crooked Hillary from rigging the election” could feasibly single out any number of voters without any evidence to offer, and try to keep those voters from casting a ballot by calling into question their eligibility.

These challenges, furthermore, can “be based on race, ethnicity and language,” according to Weiser—in part owing to their inception during the Reconstruction Era. “A lot of these laws were passed as a package to keep newly enfranchised African Americans from going to the polls,” said Weiser.

Ultimately, much of the decision-making rests in the hands of election officials, many of whom are volunteers or retirees.

This presents a further set of problems.