For his final question at the first presidential debate on September 26, the moderator, Lester Holt, asked Hillary Clinton and Donald Trump if they would respect the outcome of the election if their opponent won. That such a question was necessary is remarkable—never in recent memory has a US presidential candidate appeared liable to deny the validity of the election’s outcome.

A host of factors—not the least of which is widespread antipathy for the political “establishment”—have collectively made the United States more susceptible to authoritarian rhetoric than perhaps it has ever been. Trump has seized upon this unique vulnerability. Many experts say the Trump phenomenon is disturbingly reminiscent of times in other countries when a populist figure rode a wave of anti-government sentiment to power and subverted democratic institutions.

“Our democracy rests on people who lose the election accepting the outcome,” said Deborah Schildkraut, Chair of the Political Science Department and Professor at Tufts. “And that has, for much of our history, been fairly predictable.” Throughout his campaign, Trump has often claimed this election is “rigged” against him. Though he told Holt he would “absolutely” recognize Clinton’s legitimacy as president if she won, he has since hinted otherwise. At a speech in Florida on October 13, Trump told the audience, “This election will determine whether we are a free nation or whether we have only the illusion of democracy, but are in fact controlled by a small handful of global special interests rigging the system, and our system is rigged.”

Trump, of course, has no evidence that the election will be “rigged.” By claiming the outcome will be illegitimate if he loses, Trump is invalidating the entire political apparatus, argued Consuelo Cruz, a professor of comparative and Latin American politics at Tufts. In the United States we have a political representative democracy, not a direct democracy, she explained, which means the processes and institutions of that representation have to be seen as legitimate for democracy to function. When populist leaders gain initial support by vilifying establishment politicians and portraying themselves as anti-politicians, as Trump has done, “what happens is you are now de-legitimating the personnel and you can take the next step to claim that the system is rigged, that the processes of political representative democracy are corrupt,” she said. “Once you’ve done that, you’ve laid the groundwork for even violent politics, violent anti-system politics. And you’ve laid the groundwork to then repudiate—if you lose the election—to repudiate the winner.”

Democracy has never been a partisan issue. Presidential candidates may disagree on issues but rarely question the actual scaffolding of the political system. “My fear is that [Trump is] laying the precedent for not conceding,” said Simon Rosenberg, a Political Science professor at Tufts and the founder of the New Democrat Network.

Trump has deliberately eroded the public’s trust in basic tenets of the American political system. “He’s now attacking every single institution that exists,” said Rosenberg. “Voting, media, the debate commission; go down the list and he’s attacking everything.” In September, Trump questioned the autonomy of the Federal Reserve, telling CNBC that Federal Reserve Chair Janet Yellen is “obviously political and she’s doing what Obama wants her to do.” There is no evidence the White House has intervened in the Federal Reserve.

Trump entered politics by advocating the birtherism movement that wrongly questioned President Obama’s citizenship and knowingly spread misinformation throughout his time in office. In this campaign, Trump has capitalized on an increasingly fact-averse, conspiratorial conservative faction—nearly half of his supporters distrust the economic data released by the federal government, compared to just five percent of Clinton supporters. “It’s not like you’re going to start with, ‘We’re going to destroy the whole of democracy, and the democratic institutions are either going to be strong enough to withstand it [or they won’t],’” said Cruz. “You do it battle by battle.” Anti-system populists have employed this tactic in Latin America and elsewhere, she said. “You begin calling into question the truthfulness, the legitimacy of particular institutions. You weaken them one by one.”

The particular social and political forces that have allowed Trump to reach the doorstep of the White House parallel the conditions of other countries soon before their democracies succumbed to populist dictators, said Cruz. Extraordinary political polarization, waning faith in the existing political system, and growing contempt among conservatives for progressivism and minorities or elites are all social symptoms that may contribute to the rise of populist leaders.

“Chile and Uruguay, in the 1970s, early 70s, had for decades and decades become completely established as very strong democracies, constitutionalist democracies,” Cruz said, “whose institutions were so well established, and so consolidated, that the idea of an authoritarian regime was utterly unimaginable. And yet in the 1970s they both fell to authoritarian regimes because they were so polarized and because there was so much fear of the ‘other,’ and so much fear of insurgents.” Trump has fanned similar racial and cultural anxieties and exploited the public’s resentment of the political class.

“People’s evaluation of their own party has been fairly stable over several decades,” said Schildkraut, who specializes in public opinion, but “evaluation of the other party has gotten worse. And so to the extent that that continues, then you run the risk of seeing the other side as illegitimate, of being corrupt, not believing anything they say. And that’s a real concern because once you lose the idea that your opposition is legitimate opposition then these existential threats become more of a possibility.”

Trump has also shown a flagrant disregard for constitutional law and democratic norms, said Rosenberg. For instance, he has suggested he would imprison political adversaries and place limits on the freedom of the press as president. A page on his website allows supporters to “Volunteer to be a Trump Election Observer” with instructions explaining that volunteers will do “everything that we are legally allowed to do to stop crooked Hillary from rigging this election.” For a candidate to promote such anti-government civilian mobilization is unprecedented. “People laugh at the possibility of Brown Shirts in this country,” said Cruz.

In all likelihood, Trump will lose on November 8. But that a man with such patently authoritarian tendencies has been so popular is a bad sign for American democracy, said Cruz. “He seems to have a floor of 35 percent [of the electorate] that can sometimes grow to 40 percent, 42 percent—that’s an enormous amount in an advanced democracy like the United States,” she said. “There’s a saying among political scientists that democracies can, and often do, commit suicide. But if they do, it’s not as if they do it with a gunshot to the head. It’s more like a slow poison. You do it gradually. I’m afraid, because even if Hillary wins, that this 35 percent is going to be very unhappy.”

No one knows what Trump and the forces that contributed to his rise mean for the future of American democracy, and the optimism of experts varies significantly.

Schildkraut believes the diffusion of power in our system and the significant political autonomy of the states makes a dictatorship unlikely. “That’s not to say presidents have never overreached or used their power to do things that were undemocratic—they certainly have,” she said. “But it’s a constant back and forth between the different levels of government and the different lines of authority, and that will always be there.”

Paul Joseph, a professor of political sociology at Tufts, agreed. “I’m pretty optimistic about the United States, even though I’m a critic of the policies of the United States,” he said. “I’m optimistic about American opinion.”

David Ekbladh, a Tufts professor of American history, said, “Personally, I sometimes think a strength of the US is that nagging feeling we’re always on the cusp of decline—something baked into the 18th century concept of republicanism that the US is based upon.”

But Cruz argued that political scientists who didn’t live through an authoritarian takeover firsthand like she did are failing to appreciate the gravity of Trump’s success. From the moment she saw him dramatically descend the escalator in Trump Tower for his presidential announcement in June of last year, she said, something about this candidate felt all too familiar. He has stirred something in this country that will not soon disappear. “Once the election is over, let’s for a moment assume Clinton is victorious. This is not over,” she said. “This is just not over. This is just the beginning.”