That hasn’t deterred Mr. Kobach or his fellow travelers, who have been on their quixotic crusade for years. Until now, the damage they have done has been mostly local — fostering voter-suppression measures in states like North Carolina and Texas targeting minorities and other Democratic-leaning groups. But thanks to a president with a fragile ego and a bottomless appetite for conspiracy theories, they have weaponized their paranoia at the federal level.

On Saturday, Mr. Trump tweeted a familiar refrain at the states that refused to comply with the commission’s request: “What are they trying to hide?” The most convincing answer to that comes not from voting-rights advocates but from state and local election officials, Republican and Democratic, who oversee the actual mechanics of voting and who are best positioned to identify any fraud. Over and over, these officials, in no coordination with one another, have attested to the integrity of their elections.

The better question is what Mr. Trump and his allies so desperately hope to find. Remember that the commission was reverse-engineered to provide a veneer of legitimacy to Mr. Trump’s bogus claims that millions of noncitizens voted in 2016 — his explanation for losing the popular vote to Hillary Clinton by almost three million. (One would think that sitting in the Oval Office might have eased his pain.) But the circumstances of its creation are secondary to its real goal — to make voting harder for millions of Americans, on the understanding that Republicans win more elections when fewer people vote. According to the election-law expert Rick Hasen, the commission will probably aim to roll back parts of the National Voter Registration Act of 1993, also known as the motor-voter law, which has registered millions of voters.

The real problem, of course, isn’t fraud. It’s low turnout — in a good year, nearly half of all eligible American citizens fail to vote. As the nation marks 241 years of independence, the most pressing voting issue should be getting those tens of millions of nonparticipating Americans registered and to the polls, so that their voices can be heard. If the paranoid voter-fraud crusaders devoted a fraction of their inquisitorial energy to solving that vexing problem, now that would be something to celebrate.