There was a moment in the second presidential debate that was so uncharted in American political history that it bears repeating: Donald Trump threatened to sic a special prosecutor on Hillary Clinton and jail her if he wins.

That chilling moment stood out even in one of the most dizzying weeks of a dizzying campaign, with Trump caught on tape bragging about groping women, numerous women coming forward to confirm he groped them, and him denying that these particular women were attractive enough for him to have groped. He also managed to insinuate that he didn’t find Clinton all that attractive either, and he openly wondered why women weren’t making similar sexual misconduct allegations about President Obama.

Former Republican Attorney General Michael Mukasey called Trump’s debate barb that Clinton would be in jail if he were president a “watershed moment.” The New York Times wrote this week how Trump’s mere suggestion of locking up his political opponents reminded political scientists, not of American democracy, but of “troubled democracies abroad” in Venezuela and Zimbabwe.

Historians who spoke with TPM about the way in which this election has defied the norms of presidential politics cited it as one of the starkest ways in which 2016 has– perhaps irreversibly– redefined our country’s democratic system, but not the only one.

In so many ways, this election has been unprecedented. When was the last time a presidential candidate had such an utter disregard for facts that could so easily be fact checked? When was there a presidential candidate who was so widely rebuked by so many in his own party? When was the last time that the U.S. was accusing a foreign actor of attempting to intervene in the country’s presidential election?

Each of these departures from the conventions of presidential politics is in its own way remarkable and even shocking. But Trump goes beyond being merely unconventional. He is unmoored from the underlying democratic traditions in specific, well-understood, and troubling ways. And that is what frightens the experts.

The Big Lie

Over and over again in his campaign, Trump has gone for the “big lie,” the kind of larger than life fib that goes beyond the normal spinning that happens in every political campaign, said Ken Osgood, a history professor at the Colorado School of Mines who studies propaganda.

“This level of relying on wholesale fabrications is unprecedented,” Osgood said. “What Trump is doing very closely parallels the approach that Adolf Hitler used in his propaganda campaigns.”

Osgood said Trump has a “wanton disregard for the truth.” He tells lies that are ridiculous and easily disproven. Often times, the lies are fact checked, and yet Trump insists upon them. They are repeated en masse by his loyal supporters.

Trump says things like “thousands” of Muslims celebrated in New Jersey after 9-11 and that he saw it on TV even though no such clip exists. He insists that the Central Park Five might still be guilty even though DNA proof cleared them of the brutal rape in a racially charged case. Trump blamed the sexual misconduct allegations against him on a conspiracy of global corporate/banking/media elites – familiar anti-Semitic tropes – that has the Clintons at its center, even though Trump himself was caught on tape admitting in 2005 that he grabbed women by the genitals.

The concept of the big lie is often attributed to Hitler, who in Mein Kampf accused Jews of propagating a big lie against Germany in the 1930s. (A virtual cottage industry on the internet sustains an ongoing debate over the term’s true meaning and origins.) Accusations of a “big lie” are not new to American political campaigns, but as Osgood explains it what distinguishes the “big lie” as a propaganda tool is the sheer scale it. In order to be believable a leader cannot just tell small lies that everyone recognizes are part of human nature. He or she has to tell the kinds of lies that individuals do not recognize in themselves and therefore assume must be true.

“This whole idea of the ‘big lie’ is pretty striking, and that is the heart of what he has been relying on,” Osgood said.

Russia-Sanctioned Efforts To Influence This Election

Throughout the election, Trump’s own financial ties to Russia, his rhetoric toward Russian President Vladimir Putin and his aides ties to the country have been the focus on intense scrutiny.

It’s why when he encouraged Russian espionage over the summer it was so striking.

“Russia, if you’re listening, I hope you’re able to find the 30,000 emails that are missing,” Trump said during a press conference in July. “I think you will probably be rewarded mightily by our press.”

The fact that the U.S. is now dealing with serious allegations that the Russian government has tried to influence the U.S. election by hacking Democratic emails is a stunning development given Trump’s bizarre relationship with the foreign power.

“If this happened in the Cold War period, there would be a shit storm if we found this out,” Osgood said, noting that politicians on both sides of the aisle would be lining up to disavow the Russians. “We are just rolling over and taking it. Notwithstanding the Obama Administration.”

Making matters even more alarming, Trump – despite getting intelligence briefings–himself has cast doubt on the U.S. intelligence communities assessment that the evidence strongly suggests Russia is responsible for the hacks.

Trump Is Convincing His Supporters That This Election Will Be Rigged

Losing sucks.

But we don’t typically mess around with calling into question the legitimacy of our elections. Historians who spoke with TPM Trump stirring doubt about the outcome of the election with his base has been one of the most troubling aspects of the election to watch. And, they warn, it may be the hardest part to recover from.

“I don’t know where all that popular discontent goes,” said Laura Belmonte, a history professor at Oklahoma State University who has also specialized in propaganda. “You have people who are being encouraged to think this system is rigged. Where do we go if they feel the legitimate system has been compromised? Do they then turn on the system itself?”

Michael Kazin, a professor of history at Georgetown, told TPM that “the real danger I think is that some people who vote for him will think he really did win or he should have won ,and was treated unfairly and they continue to put forward that idea and narrative. That can be dangerous depending on what they do with it.”

Kazin told TPM that after the election, it will be important for all of the parties involved – both Clinton and Trump– to publicly accept the results of the election. After what Trump has told his supporters about a “rigged election,” it will fall to leaders to reassure voters that the integrity of the election was protected.

That could, of course, be problematic if Trump continues to tell his supporters that the election was rigged. That creates all kinds of fallout. It casts doubt on the very system the country was founded on.

Optimistically, historians say they hope the norm-defying election will be just a blip on the radar. The United States corrected course after other dark chapters in its history. But they aren’t so sure. Historians, by nature, are a bit skittish about predicting the future.

“The optimistic view would be that if you look at the pattern of American history, there have been lots of ugly episodes. We had anti-immigration sentiment that was quite nasty at the beginning of the twentieth century, there was McCarthy, Japanese internment and Vietnam,” Osgood said. “That suggests that there is a capacity for healing in the American spirit. We can kind of recognize that we have been doing things that are unsightly and adjust. There is this capacity for reflection and sobering up. But on the other hand there are some really worrying signs about what we are seeing in this current climate.”