“I will look at it at the time.” To judge by the responses of prominent conservatives, these are the most shocking words ever spoken at a Presidential debate. “Donald Trump saying that he might not accept election results is beyond the pale,” commented Arizona Senator Jeff Flake, as if the Republican nominee had finally gone too far.

In his third match-up with Hillary Clinton, Trump described babies being ripped from their mothers’ wombs and vowed to make it illegal to have an abortion. He implied that the Iraqi army and the Peshmerga are laying siege to Mosul to make Clinton look good, once again admitted paying no income tax and called his opponent a “nasty woman” who should never have been allowed to run for president.

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None of this made headlines. Instead, reports focused on Trump’s refusal to promise a concession speech if he is defeated on November 8. “What I’m saying is that I will tell you at the time. I’ll keep you in suspense, OK?” he told moderator Chris Wallace.

Wall Street Journal columnist Bret Stephens called this “the most disgraceful statement by a Presidential candidate in 160 years.” Even talk show host Laura Ingraham, a Trump loyalist, felt he had crossed a line. “He should have said he would accept the results of the election. There is no other option unless we're in a recount again,” she wrote.

This ginned-up outrage conveniently ignores the recent history of the Republican Party. Mainstream conservatives have been disputing the legitimacy of Barack Obama’s presidency throughout his eight years in office. Alleging widespread voter fraud based on the thinnest of evidence is a standard electoral tactic in states controlled by the party. Trump is an opportunist tuned in to the right’s radio signal, not an ideologue.

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Trump did more than anyone to promote the notion that Barack Obama was not born in the United States, but he was spreading an existing conspiracy theory. He threatened to jail Clinton, but Republicans have been calling her a criminal since her husband’s administration. Banning Muslims from entering the United States, building a wall to keep immigrants out, deporting every undocumented migrant in the country - these are all very familiar ideas to conservative talk radio listeners, and have been for many years.

So when Trump refers to “our president, quote ‘president,’” at rallies, employing his fingers as inverted commas, he is a chimpanzee using sign language taught to him by his handlers. When he quotes a Pew study that found 1.8 million dead people still on the electoral register, he is merely confirming the suspicion among Republicans, nurtured by elected leaders, Fox News and a network of alt-right websites, that Democrats can only win by sending an army of zombie voters to the polls.

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In a recent ABC survey, 69 per cent of Trump supporters said they believe that there is widespread electoral fraud. In a Morning Consult poll, 73 per cent of Republicans said they were worried the election could be “rigged”. Earlier this year, Gallup found that 95 per cent of Republican and 63 per cent of Democrats favour laws requiring voters to display identity cards at the polling station, even though no-one has ever been able to produce convincing evidence of more than a handful of cases of voter impersonation.

Under George W. Bush, the Justice Department spent five years looking for voter fraud and came up with nothing of any substance. In the most comprehensive analysis of electoral fraud reports and prosecutions to date, Loyola Law School Professor Justin Levitt found 31 credible instances of fraud among more than one billion ballots cast between 2000 and 2014.

The real conspiracy to “rig” the Presidential election is occurring in Republican state legislatures. In 2013, the Supreme Court struck down a crucial section of the Voting Rights Act that required states with a history of racial discrimination to clear all changes to the way elections are conducted with the federal government. Seventeen states have since passed laws making it harder to vote, often with nakedly discriminatory intent.

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Most of these so-called Voter ID laws are based on a draft drawn up by the American Legislative Exchange Council, a conservative think tank. They vary in scope, but generally require identification cards that younger voters and minorities are less likely to have. In Texas, for instance, a gun permit is considered acceptable identification but a student card is not.

In North Carolina, a swing state where the margin of victory has been under 100,000 votes in the last two presidential elections, staff working for Republican legislators asked the board of elections to provide voting data broken down by race. They discovered that African-Americans were more likely to take advantage of early voting and less likely to own a drivers’ licence, and crafted voting ordinances accordingly.

Striking down the state’s Voter ID law in July, federal appeals court judge Diana Motz stated: “Politics as usual cannot be accepted where politics as usual translates into race-based discrimination,” adding that the law targeted black voters “with almost surgical precision”.

In their more candid moments, Republican operatives have admitted to passing legislation with partisan intent. Wisconsin Representative Glenn Grothmann predicted that requiring identification at the polls would harm Clinton’s chances of winning the state. In Florida, former Republican Party Chairman Jim Greer told the Palm Beach Post that consultants “never came in to see me and tell me we had a fraud issue. It’s all a marketing ploy.”

Email correspondence leaked to the Guardian showed supporters of Wisconsin’s Republican Governor Scott Walker worrying that a conservative judge was headed for defeat in an election to the state’s Supreme Court. “Do we need to start messaging ‘widespread reports of election fraud’ so we are positively set up for the recount regardless of the final number?” asked Steve Baas, of the Metropolitan Milwaukee Chamber of Commerce. “I obviously think we should.”

“Yes. Anything fishy should be highlighted,” responded political strategist Scott Jensen. “Stories should be solicited by talk radio hosts.” A month later, Wisconsin passed a Voter ID law. Up to 300,000 people could be disenfranchised by the legislation. African-American and Hispanic voters are roughly twice as likely as whites to lack the required identification.

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Trump’s claims that the election could be rigged have been thoroughly debunked. Legal firm Ashby Law posted a 32-part rebuttal on Twitter, observing that a conspiracy to flip Pennsylvania or Ohio or Florida into Clinton’s column would require the connivance of Republicans running the board of elections, plus electoral officials from both parties at multiple polling stations. Countless volunteer poll watchers and lawyers employed by parties to scrutinise the returns would need to be tricked or turn a blind eye.

Ohio’s Republican secretary of state, John Husted, flatly contradicted Trump. I am in charge of elections in Ohio, and they're not going to be rigged,” he told CNN. “In places like Ohio, we make it easy to vote and hard to cheat.” This is a favourite line. Husted spent much of his summer in court, arguing for restrictions that would make it more difficult to register and more difficult to vote. Most were struck down.

The further Trump slips behind, the more vociferously he complains that he never had a chance. It is unprecedented for a Presidential nominee to say that he may dispute the outcome, but only in the narrowest sense. Republicans have been seeking to restrict the franchise and challenging the validity of African-American votes since the passage of the Voting Rights Act in 1965.

When Trump describes the election as “one big fix” and mutters about the need to watch “other communities” in Philadelphia, St Louis and Chicago, he can follow the warning with “everyone knows what I’m talking about,” safe in the knowledge that his supporters do. They have been hearing and reading baseless allegations of voter fraud for years.

“This is my prediction,” Trump voter Joe Cecil told the Boston Globe at a rally in Cincinnati, Ohio. “Trump is going to win the popular vote by a landslide, and the Electoral College will elect Hillary, because of all the corruption.”

“We’re going to have a revolution and take them out of office if that’s what it takes,” said Dan Bowman. “There’s going to be a lot of bloodshed… I would do whatever I can for my country.” On public Facebook pages maintained by militia groups, this is a common sentiment.

Trump’s confidant Roger Stone is setting up an informal exit poll in cities with high minority turnout, staffed by Citizens For Trump, ostensibly to prevent precincts submitting “rigged” returns. Whether this constitutes voter intimidation, a criminal offence, will depend on the actions of the volunteers and the attitude of local police and prosecutors.

The Republican National Committee is barred from mounting any such “ballot integrity” efforts by a court order imposed in 1982, in response to reports of voter intimidation, including off-duty cops patrolling outside polling stations.

At the third debate, Clinton pointed out that Trump alleges foul play every time he loses. “He lost the Iowa caucus. He lost the Wisconsin primary. He said the Republican primary was rigged against him,” she said. “There was even a time when he didn’t get an Emmy for his TV program three years in a row and he started tweeting that the Emmys were rigged against him.”

“Should have gotten it,” retorted Trump, to much mirth in the hall.

Trump is the sorest of losers, but to dismiss him as such misses the point. On the pretence of protecting the integrity of the ballot box, his party has engaged in a decades-long, ongoing effort to suppress the African-American and Hispanic vote. Eventually, Republicans will be forced to concede that if they can only win Presidential elections by preventing people from voting, it is not the messenger that is to blame, but the message.