President Trump has claimed repeatedly and falsely that voter fraud, rather than voter preference, robbed him of the popular vote last fall. And even though experts have debunked his claims, he’s now calling for a major investigation of November’s elections.

The kind of investigation Trump is calling for already happened: In 2002, George W. Bush’s administration conducted a comprehensive five-year study and found little to no evidence of widespread voter fraud. Recent examinations have come to similar conclusions, with a 2016 study finding that voter fraud is not a persistent problem.

So why does Trump continue to make such claims when they have been repeatedly demonstrated to be false, even by members of his own party? Simple: Because claims of voter fraud offer a seemingly legitimate justification for enacting restrictive voting laws that have the effect of making it harder for people to vote, particularly people of color who are statistically likely to vote for Democrats.

In places like my home state of North Carolina, unproven and unspecific allegations of voter fraud formed the basis for sweeping legislation that placed onerous restrictions on voting. The new law required voters to provide a state-issued identification to cast a ballot, limited the number of early voting days and eliminated same-day voter registration. In North Carolina and elsewhere, these kinds of restrictions have a documented disproportionate effect on voters of color, particularly African American voters. In other words, widespread allegations of voter fraud provide a vehicle to do indirectly what cannot legally be done directly anymore — limit the number of voters of color who turn out at the polls.

As an election protection volunteer for the Lawyers’ Committee for Civil Rights Under the Law during the 2016 primary and general elections, I saw firsthand how these restrictions made it difficult for voters to exercise their rights. The primary was the first statewide election conducted under the new law. As I assisted in monitoring the polls, I witnessed one African American woman in her 90s recount the days when she was barred by law from voting, eagerly show me her identification and ask me to make sure that she would be able to vote in what might be her last presidential race. I also came across people who were confused about what they needed to do to vote or unsure where they should go, and some were turned away for not having the appropriate form of identification. Many of these people were also African American. I saw one young black man who was turned away because he did not have an acceptable form of identification. I encouraged him to correct the problem so that he could vote in the general election. He said he would, but the damage of being turned away from the polls was already done. The atmosphere created by the restrictions was particularly troubling in light of North Carolina’s not so distant history of voter suppression.

By the general election, North Carolina’s voting restrictions were struck down by a federal court, which found that the legislation unlawfully and intentionally “target[ed] African-Americans with almost surgical precision” for the purpose of suppressing black voter turnout. But their effect lingered. During the general election, I observed voters who were unaware that the restrictions were no longer in place. Several stood in line with their identification visible, ready to show so that they could vote. Others asked skittishly if they would be permitted to do same-day registration because they were unsure if they could.

How many people, particularly voters of color, stayed home altogether because they were discouraged from voting because of the restrictions that were in place during the primaries? Black turnout in North Carolina went down remarkably from 2012 to 2016, with evidence suggesting that the restrictive voting legislation in North Carolina played a role. In counties that elected to limit early voting periods in North Carolina, black turnout declined by 9 percent overall during the early voting period. While black turnout rebounded somewhat on Election Day, there was still an overall drop from 70 percent of all registered black voters in 2012 to 64 percent in 2016.

Our experience in North Carolina might soon be replicated nationwide. The record here was replete with direct evidence of intentional discrimination, including legislative requests for data on the voting habits of various racial groups. The law here, therefore, was easier to strike down as unlawful because the racial motivation behind it was laid out so openly. In many other cases challenging voting restrictions that are premised on charges of fraud, evidence of intentional discrimination is rare. Instead, the ostensibly race-neutral goal of rooting out fraud has in several cases passed constitutional muster and been used as a legitimate rationale for enacting legislation that has the same effect as North Carolina’s: limiting the ability of minorities to vote, resulting in an increase in the voter participation gap between white and minority voters, which arguably gives a tremendous advantage to Republican candidates given the tendency of minority voters to vote Democrat.

Seen in this context, Trump’s call for a comprehensive investigation of voter fraud — fraud which has been shown, again and again, not to exist — is all the more chilling. Trump himself acknowledged that his beliefs are based on anecdotal evidence (and worse, false anecdotal evidence) regarding “illegal” Latino immigrants being permitted to vote. A national investigation will likely mean that the U.S. Department of Justice, the agency charged with protecting against voter suppression, will instead be asked to investigate bogus claims that have proven time and time again not to be credible. A national investigation may spur more states to enact restrictive voting legislation, and this time, the Justice Department won’t intervene to protect against those efforts. Finally, the Trump administration, with the assistance of Congress, could also use the national investigation as a basis to enact restrictive voting laws governing federal elections.

The president’s continuous calls to investigate voter fraud cannot be taken lightly. Instead, we should see them for what they are: a loud, ear-piercing dog-whistle that not only undermines the legitimacy of the American democracy, but also threatens to provide cover for restrictive voting laws that have disenfranchise large numbers of voters of color.