Republican presidential nominee Donald Trump told supporters in Columbus, Ohio, Aug. 1 that he worries the Nov. 8 election "is going to be rigged." (The Washington Post)

DONALD TRUMP has peddled a variety of conspiracy theories over the course of his noxious campaign, but his latest one is among the most destructive: The GOP presidential nominee has been claiming this week that the election may be “rigged” against him. Down in the polls, Mr. Trump might not see any cost to this preemptive effort to save face — even if he wins, he can claim he prevailed despite all of this phantom rigging. But society will pay. Mr. Trump’s incitements could easily lead to post-election disorder. Even if they do not, they erode faith in the nation’s democratic order.

Mr. Trump’s accusations do not come out of nowhere. Republicans, particularly at the state level, have for years pumped up fears of voter fraud in order to impose burdensome voter-ID laws. More recently, Sen. Bernie Sanders (I-Vt.) encouraged his supporters to believe the Democratic primary process was fixed, along with much else in society. His most zealous acolytes used this as pretext to obnoxiously and continually interrupt the Democratic National Convention last week. Little wonder that, even before Mr. Trump started talking about fraud, polling showed Americans’ trust in the electoral system to be dropping.

As with many self-serving delusions, most tales about election-stealing hang by a thread of plausibility. But that thread breaks when the weight of evidence is applied. So it is with Mr. Trump’s claims this week.

Mr. Trump’s theory is that supporters of his Democratic rival, Hillary Clinton, will flood polling places and vote multiple times, because courts have recently repudiated restrictive voter-ID laws in various states that might have prevented such cheating. “We may have people vote 10 times,” he warned in a Tuesday interview with The Post.

In fact, studies suggest the integrity of the nation’s elections is strong. A comprehensive analysis from Arizona State University’s News21 project found only 2,068 accusations of voter fraud between 2000 and 2012. A mere 7.4 percent of those involved double voting. Voter impersonation, the sort of fraud that voter-ID laws are designed to combat, accounted for 0.5 percent of recorded fraud allegations. The United States runs one of the cleanest election systems in the world. There simply is no national voting fraud crisis.

The electoral system’s biggest problems involve unnecessarily limited access to the franchise — gratuitous bureaucratic requirements, clumsy registration systems, long lines, poorly trained election workers, confusing ballots and so forth.

Mr. Trump has upended political decorum in so many ways this election year that it is sobering to imagine what he can do if he keeps inflating his election-rigging myth. He has already given the nation a sense of the dangerous places he might go. “We should have a revolution in this country!” he tweeted on election night in 2012, as he speculated that President Obama might lose the popular vote but win the electoral college vote, which is what George W. Bush did in 2000. “This election is a total sham and a travesty. We are not a democracy!” At the time, he was just a cranky billionaire TV star whom most Americans could safely ignore. Now he is a major-party presidential nominee with a large portion of the country in his thrall.