Donald Trump protesters gather in front of his campaign headquarters at Trump Tower in Manhattan. (Yana Paskova/For The Washington Post)

If anyone is rigging the election against Donald Trump, it’s Donald Trump — by disempowering his own voters.

Yes, Trump once (accidentally, presumably) told rally-goers to “make sure you get out and vote Nov. 28,” which would be 20 days after the polls close. But that isolated goof isn’t what will do him in. Instead, it’s the fact that he has told his supporters, repeatedly, that the election is “rigged” by a vast global conspiracy that will never let him win — i.e., his own supporters might as well stay home even if they do know the correct election date.

In other words, his claims that he’s doomed to lose could become a self-fulfilling prophecy.

At Wednesday’s debate and over several previous weeks — not just coincidentally, corresponding with his downward slide in the polls — Trump has repeatedly suggested that the election results will be less than kosher.

The exact nature of this tref-ness varies. He has argued that an international pan-media-banker-Democratic-FBI-elite alliance is behind unspecified improprieties. At other times he has claimed that Mexican nationals are pouring over the border to illegally cast ballots for Hillary Clinton, and that her most loyal voter base might just be dead people.

Republican presidential nominee said he will accept the results of the election if he wins, at a rally on Oct. 20 in Delaware, Ohio. (The Washington Post)

Such charges will rile up some of his base, including those who want to “monitor” the polls so they can intimidate anyone resembling, as one acolyte put it, “Mexicans. Syrians. People who can’t speak American.” These hardly seem like idle threats; data from the World Values Survey show a correlation between belief that election officials are unfair and violence at the polls.

But however motivating this rhetoric may be for a handful of die-hard Trump thugs, the larger effect will probably be to depress turnout among more marginal voters — who disproportionately comprise Trump’s base.

Several recent social science studies find that belief in government corruption seems to discourage voting. An Innovations for Poverty Action field experiment in Mexico found that telling residents about the incumbent party’s record of corruption depressed their turnout rates.

“They stayed home because they were fed up with the system,” said Alberto Chong, a Georgia State University professor who co-wrote the paper.

A second study, from scholars at Sweden’s University of Gothenburg, used a multiple-country analysis to show that perceptions of government malfeasance negatively affect turnout. This is true, however, only in countries with low to medium levels of corruption (like, say, the United States).

In another experiment, this time in the United States, researchers tested different messages shown to people Googling information about voter registration. Language saying “the system is rigged” was less effective at getting clicks than “registering is quick, easy, and free.”

The voters most likely to be turned off by rhetoric about a rigged system are those least engaged in politics and most on the fence, said Adam S. Levine, a Cornell University professor and co-author of the third paper.

Levine says that Trump’s claims of political and electoral system corruption are most likely to be seen as credible and convincing by Trump’s own followers — the very constituency he should be trying to convince of its political efficacy.

Indeed, Trump supporters are already much less likely to believe that their votes will be counted accurately than are Clinton’s backers, or even than supporters of previous Republican presidential candidates.

An August poll from the Pew Research Center found that only 11 percent of registered voters who said they supported Trump were “very confident” that vote tallies nationwide would be counted accurately; this is about a fifth of the share of Clinton voters who said the same.

As for whether their own votes would be counted accurately, 38 percent of Trump voters said they were very confident this would happen. In 2008, nearly twice as many John McCain voters (65 percent) had great faith that their votes would be counted accurately.

Many demographics — women, Muslims, immigrants, Hispanics, African Americans, people with disabilities — have been harmed by Trump this campaign. But perhaps his greatest betrayal has been to his own supporters, the economically anxious, white working-class voters who he says have been forsaken by the rest of the political class. He alone can help them, he asserts.

Trump has made cruel promises to his supporters that he cannot keep, about reopened factories and mines; he has sown fear and mistrust among these constituents and their neighbors. And now he is hell-bent on convincing them the system is so rigged, so broken, that they no longer have any political agency in choosing their president or anyone else who might be on the ballot next month.

Rather than motivating his supporters to make sure their voices are heard, he is leading them into silence.