There was only one moment that really mattered during the final presidential debate: Donald Trump said that he might not accept the results of the November election.

It wasn’t Trump’s first assault on democracy, or on the legitimacy of his opponent. Trump has often been a little too comfortable with the idea of using violence to get his way, and a little too willing to egg on his followers’ worst instincts.

But the last weeks of the campaign, as his chances fade, have made Trump more desperate, less careful, and more dangerous. During the first debate, he promised to accept a Clinton win. During the second debate, he “joked” — not really joking — that she’d better hope she won, because if he won he’d put her in jail. By the third debate, he simply reneged on his earlier promise: “I will look at it at the time,” he said when asked if he’d accept the election results. “What I’ve seen is so bad.”

Warned by moderator Chris Wallace that he was coming dangerously close to smashing centuries of American history, marked by the peaceful transfer of power, he simply smirked: “I’ll keep you in suspense.”

Over the course of his improbably successful presidential campaign, Trump has often given the impression that he’s playing with fire: that he is invoking deep anxieties about cultural change, fear of nonwhite Americans, and a belief that society is fundamentally broken, without understanding that those sentiments are too powerful for him or anyone else to control. Now he’s opening doors that should never be opened — inviting his followers to trust him (and their own instincts) more than they trust democracy itself, and to outright challenge the outcome of the election if it doesn’t go his way.

Trump is expected to lose this election. And that loss will probably not be formally contested: The Republican National Committee has already pledged to accept the outcome regardless of winner.

That doesn’t make it more okay that he didn’t promise to concede. It makes it all the more dangerous: He’s just opened the door for someone, somewhere, to take democracy into their own hands.

WALLACE: I want to ask you here on this stage tonight do, you make the same commitment that you will absolutely, sir, that you will absolutely accept the result of this election? TRUMP: I will look at it at the time. I'm not looking at anything now. I will look at it at the time. What I've seen, what I've seen is so bad. First of all, the media is so dishonest and so corrupt. And the pile-on is so amazing. The New York Times actually wrote an article about it, that they don't even care. It's so dishonest. And they have poisoned the minds of the voters. But unfortunately for them, I think the voters are seeing through it. I think they're going to see through it. We'll find out on November 8. WALLACE: But sir — TRUMP: Excuse me, Chris, if you look at your voter rolls, you will see millions of people registered to vote. This isn't coming from me, this is coming from Pew report and other places. Millions of people that are registered to vote that shouldn't be registered to vote. So let me just give you one other thing as I talk about the corrupt media. I talk about the millions of people. I tell you one other thing. She shouldn't be allowed to run. She's guilty of a very, very serious crime. She should not be allowed to run. And just in that respect, I say it's rigged. Because she should never -- Chris, she should never have been allowed to run for the presidency based on what she did with emails and so many other things. WALLACE: Sir, there is a tradition in this country, in fact one of the prides of this country is the peaceful transition of power. And that no matter how hard-fought a campaign is, that at the end of the campaign that the loser concedes to the winner. Not saying that you're necessarily going to be the loser or the winner. But that the loser concedes to the winner, and that the country comes together in part for the good of the country. Are you saying you're not prepared now to commit to that principle? TRUMP: What I'm saying is I'll tell you at the time. I'll keep you in suspense, okay?

This is an assault on democratic norms. Period.

The entire point of a system of government like the one the United States has — whether you want to call it a democracy or a republic — is that when there is an election, the loser allows the winner to assume power. That is the assumption all participants in a democracy share, and that allows them to work together and make the democratic process happen.

It’s not “suspenseful” because when you are laying the foundation of an entire system of government — not to mention the society, the lives of 300-plus million people who rely on that government to keep them safe — you have to deal in certainty.

Obviously, this principle is totally corrupted when the election is actually not fair — when it is, if you will, rigged. But Trump isn’t setting standards for what a fair election would look like. (He couldn’t do it if he tried; voter fraud is not a real phenomenon in 21st-century America, and any standard he could name for a fair election would be a standard the US would easily hit.)

Instead, he’s pretty much conflating “a rigged election” and “an election Hillary Clinton wins.” He is making the legitimacy of an election dependent not upon the electoral process itself, but on whether he and his followers give it their stamp of approval. It is, fundamentally, a rejection of the rule of law.

Even if most of America accepts an election result, it only takes a few die-hard insurgents to cause real trouble

Trump’s claim that the only way he could lose would be a rigged election looked ridiculous enough in early September, when he was actually within striking distance of Clinton in the polls. By late October, when his odds of winning the election look more like a crapshoot than a coin flip, hinting that a Clinton win will prove the election was a fraud is flatly absurd.

To her credit, that’s exactly how Hillary Clinton made it look. Her response to Trump’s literal flirtation with undermining the pillars of democracy was an honest, straightforward, “Let me respond to that, because that’s horrifying.” But from there, she didn’t build up the threat Trump was posing; she belittled him, relentlessly, pointing out every other time he’d complained about a rigged election, right down to the voting in the Emmys.

In front of the American public, she made Donald Trump look small. She communicated that America would be strong enough, resilient enough, to deal with his temper tantrums.

As far as America as a whole is concerned, she might be right — plenty of Republicans think the election may be rigged, but faith in the election doesn’t appear to be that much lower than it was in previous cycles.

But at some level, what the American public as a whole thinks is irrelevant. What matters is what Donald Trump’s most hardcore supporters think.

There are millions of them. Many are fanatically devoted to him. Many believe that Trump is headed for a landslide victory, because that is what he is telling them. Many believe, just as Trump said during the debate, that Hillary Clinton should legally not be allowed to be president because she’s committed a crime. Many believe that Clinton and her campaign are colluding with nonwhites to rig the election.

All it takes is a few people to cause massive violence and instability. Even if only a few Trump supporters are die-hard enough to try to launch a coup on a Clinton presidency, or to take out their anger on people who look like unauthorized immigrants, there are more than a few Trump supporters in America. There are handfuls and handfuls.

It’s not only fundamentally important that Trump concede, and do his best to persuade his followers that law and order matter even when it’s not on their side. It’s fundamentally important that he do it in a way that seems uncoerced — and Donald Trump is extremely bad at reading from a script in a way that doesn’t make it obvious he’s reading from a script.

Even then, Trump might not be able to control what he’s unleashed.

In Ryan Lizza’s recent New Yorker profile of Kellyanne Conway, Trump’s campaign manager, Conway recounts how she had to tell Trump to stop shrugging about how if he lost, he’d return to his very nice life. “They so believe in you that when you say, ‘Eh, if it doesn’t work out, I’ll go back to the happy place,’ they don’t think that they will.”

There is a not-insubstantial risk of violence on Election Day, and Donald Trump is all but encouraging it

To be honest, this is all somewhat academic. We may not have to wait until the ballots are counted to reap the harvest Trump has sown.

It is totally plausible that there will be violence between Trump supporters and opponents on Election Day. It’s not certain, but it’s plausible — in a way it hasn’t been for any American election in recent memory.

Donald Trump has done absolutely nothing to quash this. In fact, he has done much to stoke it. He has routinely instructed his supporters to gather posses and go to “certain areas” where voting fraud might take place, “like Philadelphia” — in other words, areas populated by nonwhites. He has unofficially deputized them as poll watchers. He has charged them, individually, with ensuring the outcome of the election is free and fair.

This is an enormous responsibility to bear. And when people think the fate of democracy is resting on their shoulders, they’re likely to do whatever they feel is necessary to protect it.

That’s even more true when they believe that if they don’t believe an election is legitimate, it isn’t. If the election is already illegitimate, you’re not delegitimizing it by using force — you’re protecting the cause.

That’s the logic behind the US’s history of Election Day violence. It would be a shame if it caught hold again. But Donald Trump is certainly sending his followers that message.

Trump has already sent his followers all the messages they need to hear

One of the most dangerous things Donald Trump has done is give certain people license to exercise their worst, most violent impulses in the name of the greater good. He’s promised to allow police “to go and counter-attack” and to allow border patrol and immigration enforcement agents to deport immigrants at will. He’s rhapsodized about the good old days when you could just beat up a protester.

Trump has been accused of emboldening a whole spectrum of hate: everything from organized white supremacy, to schoolyard taunts, to violent hate crimes. He hasn’t necessarily inspired feelings that weren’t already there. But he’s allowed people to voice and act on them publicly and not feel ashamed.

That is a problem.

The point of living in a society is that some things really aren’t in suspense. Some things really are off the table. You cannot just do whatever you want, and in exchange, you don’t have to wake up every day and worry that you’ll be harmed because someone else is doing whatever they want.

I can’t believe I have to explain this. But a presidential candidate just responded to a question about the peaceful transition of power with “I’ll keep you in suspense,” as if it were somehow a good thing to call social fundamentals into question, so I guess I have to.

Because here’s the thing about what Trump’s doing: Ostensibly, he’s saying he’s keeping an open mind, that he’s keeping us all in suspense. But when you open doors that are not supposed to be opened, you certainly send the message that you want people to rush through.

His trajectory from the first debate to the third is clear. Trump doesn’t need to follow through all the way, to fill in all the blanks. He’s raised questions that never get raised — that shouldn’t be raised. That’s a strong signal that he thinks the answer is yes — or at least that it is okay to think the answer is yes.

It is a sick cycle. People respond to Trump because he openly voices their anxieties and fears; he emboldens them to act on those fears in public. He tells his supporters what they want to hear to make them more loyal; they become more convinced that their way is the only way.

Even if Trump turns around tomorrow and says that he will unconditionally accept the results of the election, and never mentions rigging or voter fraud again, he can’t close that door.