Donald Trump has gone back to the same message, time and time again, as he criss-crosses the United States to try to fire up his Make America Great Again base.

At nearly every campaign stop and in all-caps screeds on social media, he is unequivocal: The only way he will lose the presidential election on November 5 is if his Democratic rivals cheat.

“Now we have two things we have to do,” he told a crowd in the battleground state of Georgia in early August. “We have to vote, and we have to make sure that we stop them from cheating because they cheat like dogs.”

The former president’s false claims — widely debunked as misinformation, or outright lies — aren’t new: He’s been saying for years that the US electoral system is rife with voter fraud.

But as the election fast approaches, experts say his rhetoric is intensifying, and they warn that Trump appears poised to try to subvert the results just as he did in 2020.

“We are seeing this constant narrative that there’s something nefarious at work within our election system,” said Sophia Lin Lakin, director of the Voting Rights Project at the American Civil Liberties Union (ACLU).

The idea that there is voter fraud at play, she told Al Jazeera, could potentially cause “a lot of mischief” in the election — and most importantly, undermine its outcome.

“We saw this particular playbook before, unfortunately,” she said. “And it very much looks like there is a doubling-down of that particular strategy going on right now, in a very hyper-intensified kind of way.”

It’s unclear when Trump made his first voter fraud claim.

But even before he launched his first successful presidential bid in 2015, the former New York real estate mogul was raising doubts about election results.

In 2012, for instance, he described President Barack Obama’s victory over Republican Mitt Romney as a “sham”.

Four years later, as he ran for the 2016 Republican presidential nomination, Trump accused his rival Senator Ted Cruz of winning the Iowa caucuses through “fraud”. He demanded the vote either be nullified or held again.

“Ted Cruz didn’t win Iowa, he stole it. That is why all of the polls were so wrong and why he got far more votes than anticipated. Bad!” Trump wrote on social media at the time.

His claims of fraud didn’t stop after he won the Republican nomination, nor when he defeated Hillary Clinton in the 2016 general elections. In fact, Trump doubled down — and broadened the scope of his allegations.

For instance, while Trump won the Electoral College — the weighted voting system that ultimately determines who goes to the White House — he got fewer total votes than Clinton that November.

So just weeks after his victory, he alleged he only lost the popular vote because of “millions of people who voted illegally”.

Two years later, midway through his administration, Democrats won control of the US House of Representatives in the 2018 midterm elections.

Trump again blamed “illegal votes”. He said in an interview with The Daily Caller that voters “go to their car, put on a different hat, put on a different shirt, come in and vote again”.

But election experts have been clear: Voter fraud — that is, an attempt to unlawfully cast a ballot — is exceptionally rare in the US.

Clerical and administrative errors may occur in a process that sees tens of millions of people cast their votes across the country, but researchers have found no evidence of widespread fraud.

“Study after study conclusively shows that voter fraud is vanishingly rare,” Sara Carter, an attorney at the Brennan Center for Justice at New York University, told Al Jazeera.

“Widespread voter fraud is simply a myth. You’re more likely to be struck by lightning in the US than you are to commit voter fraud.”

The rarity of voter fraud hasn’t stopped Trump and his allies from making allegations about it some of their most prominent talking points.

And in 2020, that incendiary rhetoric reached new heights with the so-called “Big Lie”: the false claim that Democrats stole that year’s election, resulting in Trump’s loss to US President Joe Biden.

In the weeks leading up to the tightly contested vote, Trump baselessly argued that the system of mail-in voting, which was heavily relied upon during the COVID-19 pandemic, was rigged.

After his defeat, Trump told his supporters that their votes weren’t counted while “illegal votes” were. He pressured local and state officials to declare him the winner, or to refuse to certify Biden’s victory. And his team filed multiple lawsuits to try to overturn the results, all of which were rejected.

Then, on January 6, 2021, Trump told a rally in Washington, DC, to “stop the steal” — and that afternoon, a mob stormed the US Capitol in a violent insurrection that aimed to block Congress from certifying the election outcome.

Trump and some of his closest allies have since been criminally charged for their campaign to overturn the 2020 vote. The ex-president denies any wrongdoing.

Yet while the “Big Lie” has been repeatedly rebuffed by experts — “it is simply a lie,” said Carter — many Americans still do not think Biden was elected fairly.

Recent polls show that about one-third of people in the US believe the 2020 election was stolen from Trump. But among Republican voters alone, that proportion jumps to about two-thirds.

Matt Gertz, a senior fellow at the nonprofit Media Matters for America, pointed to the country’s “almost entirely bifurcated” news landscape as a key reason why this belief is still so widely held.

Conservatives in the US have been told for decades that they cannot trust mainstream media, Gertz explained. And today, many get their news exclusively from right-wing outlets set up to appeal to them directly, such as Fox News, Newsmax and the One America News Network.

“The result of that is there is an immensely powerful bubble on the right, in which factual information about the election just cannot enter,” Gertz told Al Jazeera.

He added that this “bubble” was “the crucial factor in Trump’s 2020 election subversion plan”.

“He knew that he would be able to rely on an array of right-wing media figures and outlets who would support his claims or at least not debunk them to his supporters,” Gertz said of the former president.

“A broad swathe of the country has remained convinced that the 2020 election was illegitimate and is more than willing to believe Donald Trump if he says, following the election in November, that (the 2024) election was illegitimate as well.”

Trump has so far refused to say unequivocally that he will respect the results of the upcoming election, which will see him go up against Vice President Kamala Harris, the Democratic candidate.

During a presidential debate in June, he said he would accept the outcome only if “it’s a fair and legal and good election”. He then quickly added that he would have “much rather accepted” the 2020 results, too, “but the fraud and everything else was ridiculous”.

More recently, on September 7, Trump posted on his Truth Social platform that, if he wins in November, “those people that CHEATED will be prosecuted to the fullest extent of the Law, which will include long term prison sentences”.

He said that could include lawyers, donors and “corrupt election officials”, among others.

“Those involved in unscrupulous behavior will be sought out, caught, and prosecuted at levels, unfortunately, never seen before in our Country,” he wrote.

In this election cycle, much of Trump’s voter fraud narrative has focused on people who are not American citizens.

But Carter at the Brennan Center described this as a “non-issue”. Non-citizen voting is illegal under US law — incurring penalties such as imprisonment and possible deportation — and research shows it is extraordinarily rare.

Yet Republicans, who have made anti-immigrant policies a central plank of their party platform, falsely claim Democrats are allowing undocumented immigrants into the country in order to get their votes. In June, the Republican-controlled House of Representatives even passed a bill requiring proof of citizenship to cast a ballot.

The notion that the US is rife with voter fraud has become a “boogieman” of sorts, Carter explained, and Trump and his allies are using it as “a false justification for efforts to undermine valid election results”.

It is also being used to justify a wave of voting restrictions across the country.

Some states have made it harder to register to vote and cast mail-in ballots or have ushered in stricter voter identification requirements.

“The most aggressive years for restrictive voting legislation in the past decade have come after the 2020 election, and that’s not a coincidence,” Carter said.

She told Al Jazeera that Americans in 28 states are going to face curbs this November that weren’t in place the last time they voted for president. “The policies all share one thing in common,” she added, “which is that they do disproportionately burden voters of colour.”

Many of the new voting restrictions have been implemented in swing states that saw hard-fought races in 2020. These same states are expected to be close again when Trump goes up against Harris in November.

For example, Georgia and Florida have both made it harder to vote and heightened the risk of intimidation, the Brennan Center said in a recent report. North Carolina also put in place more barriers to casting a ballot.

Meanwhile, efforts to put election deniers into key positions in the US electoral system also are drawing alarm.

In the battleground state of Georgia, for instance, the state electoral board passed a new rule in August that could delay election certification — the process whereby a vote count is confirmed — if local officials raise concerns about the accuracy of the vote.

“Certification is supposed to be a ministerial process, a formality, that happens after an election is over,” said Carter. “But it has now been increasingly politicised, so that efforts to block certification are efforts to subvert election results.”

Austin Sarat, a professor of law and politics at Amherst College in Massachusetts, said many Americans have already lost faith that their votes will be counted fairly. Some believe Trump’s voter fraud claims while others are frustrated by the new barriers to voting.

That means the 2024 vote may not be decided on November 5 because its results “likely will be called into question … not just by political leaders on one side of the political spectrum but by large numbers of citizens”, he explained.

Some of the challenges to restoring trust in the system can be addressed right away, Sarat told Al Jazeera. To stamp out efforts to meddle in election certification, for example, state leaders should instruct election boards “that they have a limited and purely ministerial role to play”.

But addressing more deep-rooted problems will take longer.

“The best thing that can be done for democratic governance is for the government of the United States to address the real needs of the American people,” Sarat said. “So to restore faith in elections, you first need to restore faith in democracy.”

Lakin at the ACLU noted that, while the 2024 election season has seen a plethora of attacks on voting rights, civil rights activists and organisations are mobilising, too.

“The efforts to ensure that this doesn’t happen, to ensure that our systems are strong, to ensure that we are prepared for these kinds of assaults — that also has been ongoing in a much more intensified and organised” way, she said.

Advocates have pointed to state laws that shored up access to the ballot box in the aftermath of the 2020 election as positive steps forward.

That includes measures in Nevada that expanded voting access and legislation in Michigan that clarified the state’s election certification procedures and strengthened rules around recounts to prevent partisan interference.

Federally, rights groups say legislation such as the Freedom to Vote Act and the John R Lewis Voting Rights Advancement Act could help bolster voter protections across the country.

But the likelihood these bills will pass depends on the makeup of Congress after November.

In the meantime, experts stress that the threat of post-election chaos is real, but it remains unclear what form it could take.

“At the least I think you’ve got potential for some fairly significant chaos following the vote, and it’s hard to predict where it will go from there,” said Gertz from Media Matters.

“We are poised to see a repeat performance of the cycle that we saw that led up to January 6.”

But at the same time, Lakin said groups like the ACLU are “making sure voters get the right information, making sure they know where to go if something comes up (and) making sure they have what they need to cast a ballot”.

They will also be ready to defend voting rights in court if necessary.

“We saw these threats before, and the system held,” Lakin said. “There have been processes and safeguards put into place that will hopefully continue to hold and make this country even stronger.”