If you go to a Donald Trump rally, you never know what's going to happen.

For months, when people said this, they were referring to Trump himself. He had no teleprompter and no filter; give him an hour alone onstage and who knew what he would come up with?

But at this point, Trump's rallies aren't just unpredictable. They're out of control. And they're a threat to American democracy whether or not Trump is ultimately elected president.

On March 9, a white Trump supporter named John McGraw sucker-punched a black protester named Rakeem Jones at a rally — then threatened to kill him the next time they met. On March 19, a similar incident happened with the protesters' races reversed: A black Trump supporter punched a white protester whose sign superimposed the Confederate flag over Trump's face, then kicked the protester after he fell to the ground.

Trump's own campaign manager, Corey Lewandowski, has been accused of assaulting a reporter, and was caught on tape during the March 19 rally in Tucson, Arizona, grabbing a protester by the collar.

And the protesters themselves are getting more organized and aggressive — which, in turn, escalates the aggressiveness of Trump's supporters. On March 11, America saw the results: Trump abruptly canceled a rally in Chicago with hundreds of protesters in attendance, setting off an evening of intimidation that occasionally exploded into outright violence.

Trump has had opportunities to calm things down. Instead, a few days after McGraw was charged, he offered to pay McGraw's legal fees — carrying through with an offer he'd been making at rallies since the Iowa caucuses.

The Trump campaign is making a halfhearted effort to maintain plausible deniability. Trump has started denying he ever offered to pay anyone's legal fees; and the campaign claims that the video of Lewandowski in Tucson doesn't show exactly who grabbed the protester.

Here is Donald Trump's campaign manager in the Tucson crowd grabbing the collar of a protester. pic.twitter.com/JZ9RntWlHY — Jacqueline Alemany (@JaxAlemany) March 19, 2016

But both Trump's supporters and his protesters are hearing exactly what they need to hear. And that's a problem that threatens to reverberate far beyond the rallies at which they're playing out now.

By explicitly condoning and encouraging violence, Trump is rejecting some of the most basic social norms of discourse and democracy. These norms aren't just niceties. They are the rules we follow to make our laws and institutions work.

Now the frontrunner for a major party's nomination — the man who could very plausibly be the 45th president of the United States — is gleefully undermining them.

A would-be president who would encourage and even subsidize violence among his supporters is something new and dangerous in American politics. A president who would do such things could use the power of the presidency to terrifying ends.

Even if Trump is never elected president, his corrosive effects on democracy could be long-lasting. Trump is already telling his supporters that their loyalty to him is more important than basic norms of impartiality and justice — and throwing his immense power, as a private citizen and presidential candidate, behind them to demonstrate his sincerity. It's a very dangerous signal to send, and it's one Trump can't necessarily control.

Not that there's any indication he wants to.

Trump rallies have become a magnet for protesters — and protesters have become a magnet for violence

Occasional protesters — largely young people of color, often protesting Trump's immigration policy or rhetoric toward Muslims and Latinos — have been demonstrating at Trump rallies for as long as he's been on top of the polls. But while protests were only an occasional occurrence at first, in 2016 they've become ubiquitous.

Some events have been interrupted 10 or more times by protesters; the New York Times described "an almost constant stream of protesters" during a rally in New Orleans on March 5.

The protests haven't been the result of any unified movement. Some of the early protesters were affiliated with immigration groups; some of the more recent ones have been associated with the Black Lives Matter movement. But many haven't been affiliated with any group or clear agenda at all: What unites them is simply that they believe Donald Trump and his supporters are racist and un-American, and they're willing to interrupt his events to say so.

But Trump really doesn't like being interrupted. And his followers don't like it either. So many of the protesters at Trump rallies have been met with violence from supporters or security.

This creates a vicious cycle. The more incidents of violence against protesters, the more liberal activists become convinced that Trump is a dangerous demagogue who needs to be stopped. Thus, the more likely they become to protest — and the more interruptions, the more opportunity for violence.

Here is just a selection of the times when protesters have been physically assaulted by Trump supporters:

In addition to the incidents involving Trump supporters, of course, are the incidents involving Trump staff — namely, his campaign manager (and putative future White House chief of staff) Corey Lewandowski:

On March 8, Breitbart reporter Michelle Fields was nearly pulled to the ground after a press conference by a man identified as Lewandowski. Lewandowski and the Trump campaign reacted by denying Fields's account and trying to discredit her.

On March 19, a video showed Lewandowski and another man confronting a protester at Trump's rally in Tucson — then the man being yanked back by the collar, with an arm whose sleeve resembled Lewandowski's outfit by his neck. The Trump campaign claimed that the video showed that the man next to Lewandowski collared the protester.

Donald Trump has actively encouraged his supporters to beat people up

Every time Donald Trump is asked about violence, he says he "doesn't condone" it.

That is bullshit.

Sure, Donald Trump has never said, in order, the words "I condone violence at my rallies." But he has egged on his supporters to respond violently to protesters, and he has defended violence as a natural expression of the passion his supporters feel for the country.

Before a Trump rally, a standard announcement tells attendees not to hurt protesters, even though they've "taken advantage of Mr. Trump’s hospitality." But after Trump arrives, supporters hear a very different message.

Here is what Donald Trump said at a rally on February 1 in Cedar Rapids, Iowa (via Mediaite):

"if you see somebody getting ready to throw a tomato, knock the crap out of 'em, would you? Seriously. Okay? Just knock the hell — I promise you, I will pay for the legal fees. I promise. I promise."

Here is what Trump said at a rally on March 4 in Warren, Michigan, the day after the Kentucky protesters were assaulted (via the Associated Press):

During one interruption, Trump said, "Get him out. Try not to hurt him. If you do I’ll defend you in court." "Are Trump rallies the most fun?" he then asked the crowd. "We’re having a good time." He then recalled an incident at a New Hampshire rally where a protester started "swinging and punching." Trump said some people in the audience "took him out." "It was really amazing to watch," he said.

Here is what Donald Trump said at the March 9 Fayetteville rally at which McGraw assaulted Jones (via the Atlantic):

"See, in the good old days this didn’t use to happen, because they used to treat them very rough. We’ve become very weak."

Here is what Donald Trump said at a St. Louis rally on Friday at which police removed one protester with a bloodied face (though the circumstances of his injury are still unclear):

"Part of the problem and part of the reason it takes so long [to kick them out] is nobody wants to hurt each other anymore."

Bloodied at St. Louis Trump rally. pic.twitter.com/3O65vsktvS — Trymaine Lee (@trymainelee) March 11, 2016

Statements like these add up to a consistent message: Gee, it would be great if someone taught these protesters a lesson.

What is most disturbing, though, is how much Trump legitimizes — even embraces — acts of violence that have already occurred, connecting them to the good, "beautiful" feelings supporters have toward their country and his campaign.

This was Trump's defense of his supporters at the CNN debate on March 10:

We have 25,000, 30,000 people, they come with tremendous love and passion for the country. You're mentioning one case, I haven't seen, I heard about it, which I don't like. When they see what's going on in this country, they have anger that's unbelievable. They love this country. They don't like seeing bad trade deals, higher taxes, they don't like seeing a loss of their jobs where our jobs have just been devastated. And I know -- I mean, I see it. There is some anger. There's also great love for the country. It's a beautiful thing in many respects.

This isn't limited to violence against protesters. When asked in August about a hate crime in which two Trump supporters beat a homeless man with a metal rod, Trump said, "People who are following me are very passionate. They love this country and they want this country to be great again."

And it's not limited to violence committed by Trump supporters. After Fields accused Lewandowski of assaulting her, and other reporters took her side, Trump invited reporters to a "press conference" after the March 15 primaries at which he took no questions.

He did, however, deliberately have Lewandowski standing right beside him in a place of pride, and explicitly praised him for doing a good job — something Trump has not done after winning primaries that aren't preceded by Lewandowski yanking someone by the arm.

Trump could have just given a typical speech that didn't refer to his campaign manager one way or the other at all. And when he was asked on March 13 if he would pay McGraw's legal fees, he had an opportunity to break with his earlier rhetoric. He easily could have said that he wasn't issuing a blank check for his supporters to hurt people, just trying to defuse a particularly fraught event on the night of the Iowa caucuses.

He did not do that. He has raised his pen above the blank check and is signing on the dotted line.

Trump's supporters believe that disrupting a rally is an unacceptable violation of norms

Trump supporters believe that coming to a Trump rally to protest is an illegal and unacceptable act in its own right — that it's the protesters who are violating public order by coming into "their" space.

As far as that goes, the law is on the side of Trump supporters. Political protests aren't always protected by the First Amendment; federal and state laws impose plenty of restrictions on speech. Crucially, one of those restrictions is on events guarded by the Secret Service.

"It is a federal offense, punishable by up to 10 years in prison to protest anywhere the Secret Service might be guarding someone," Slate's Dahlia Lithwick and Raymond Vasvari wrote in 2012. That includes campaign events for major presidential candidates. It includes Trump rallies.

In fairness, protesters are rarely charged merely for protesting, much less charged with a federal crime. But they are routinely removed from the venue by police officers.

This is the standard response to protesters, whether they're protesting Barack Obama or Hillary Clinton or Ted Cruz. It's the political norm: Protesters are treated as an unwelcome disruption, but law enforcement is trusted to remove them peacefully.

Trump certainly uses the police presence at his rallies to his advantage. On multiple occasions, the Trump campaign has directed law enforcement agents to remove people who look like they might be protesters — which, unsurprisingly, tends to be people of color.

When protests do erupt, Trump uses the fact that police are taking the protester away as evidence that the protester must have been violent. And on Saturday, he promised to "start pressing charges against all these people" — threatening to "ruin the rest of their lives."

But Trump keeps implying to his supporters that the police can't really solve the problem — that what it really takes is some people willing to use their fists. That's why he offers to pay for legal fees, and reminisces warmly about previous violent responses to protesters.

His supporters are more than happy to oblige. "We all want to punch 'em. We want to see Trump. We don't want to hear the hecklers," one woman at Trump's March 12 rally in Cleveland told NPR's Don Gonyea. Another rally attendee told the Huffington Post's Igor Bobic:

"We didn’t ask for them to come. We’re here having a meeting. And they want to come disrupt it? They deserve what they get. They brought that upon themselves when they walked in that door, that hell might break out. And it did. What did they think was going to happen?"

The odd thing about Trump's rhetoric, though, is that it's based in a theory of deterrence: When he says there wouldn't even have been protesters back in the days when people were willing to "hurt each other," he implies that beating up a protester today will prevent a protest tomorrow.

That is not what has happened. At all. Violence against Trump supporters has spurred more, more coordinated, and more aggressive protests.

Chicago: a Trumpless rally that was more chaotic, if not more violent, than anything that had happened before

In retrospect, it should have been obvious that Chicago was a likely venue for protester activity. Both supporters and critics have pointed out that the city has a history of leftist organizing and large-scale protests. Some activists started organizing the day the Trump campaign announced the Chicago rally; others, like a group of students at the University of Illinois Chicago (where Trump was speaking) whose "Stop Trump" Facebook page garnered more than 1,000 likes, had started their planning in the days leading up to the event.

That advance planning collided with the rising tensions around Trump rallies after the week's events: McGraw's assault of Jones in Tennessee and Trump's response, the furor over campaign manager Lewandowski's alleged assault of Fields, and a St. Louis rally earlier on Friday where thousands of supporters and protesters alike had been kept out of the overcrowded venue, with their frustration often boiling over into shouting matches and shoving.

Battle lines drawn at Trump rally pic.twitter.com/Y9yRTnjOAm — Trymaine Lee (@trymainelee) March 11, 2016

In Chicago, the protests began before the rally did. One group of activists shut down the street outside the rally — in a simultaneous protest against Trump and against State's Attorney Anita Alvarez, who is facing a primary challenger and whom activists have targeted for her protection of police accused of killing black men. (Ironically, this street closure thwarted the plans of the student group, who were organizing a march to the venue.) Police were already arresting protesters outside the rally.

Inside the rally, meanwhile — where up to a third of the crowd were estimated to be protesters — an abrupt announcement was made at 6:30: Donald Trump would not be attending. The rally had been canceled.

Trump said he canceled the rally because he had been warned by law enforcement about protester-provoked violence. The Chicago police and University of Illinois campus police both say nothing of the kind occurred. In fact, the head of the UIC police said it was Trump's "abrupt announcement of the cancellation of the event" that was responsible for what followed.

What followed has been loosely described as "violence," or as "clashes" between protesters and supporters. In reality, the bulk of the "clashes" appear to have been shouting matches, with some degree of shoving. There was at least one fistfight, but physical violence of the sort that happened to protesters in Birmingham in November or to Jones in Fayetteville on Wednesday — in other words, the sort of violence that happens when Donald Trump does attend his rallies — doesn't appear to have been widespread when Trump wasn't there.

Much of the violence appears to have happened outside the venue, where there's evidence to suggest that the Chicago Police Department made things worse than they otherwise would have been. The New York Times reported three injuries, including one police officer (though NBC Chicago reported two police officers had been injured). Two of the four people who have been charged since the rally are protesters charged with "resisting arrest" or "obstructing an officer" — in other words, arrested for protesting.

And CBS News's Sopan Deb, who was thrown to the ground and arrested by police for filming a scuffle, offers pretty suggestive evidence that police were at least as violent with him as any supporters or protesters were with each other.

But to those who were inside the venue, the experience was terrifying. Writer Keith O'Brien, who attended the rally with the UIC student protesters, recounts in Politico Magazine:

They (Trump supporters) kept coming, surging forward. I got struck in the head with a thrown object, something hard, metal perhaps. Protesters, unaffiliated with the UIC movement, lashed out, pushing back, fighting in skirmishes with willing Trump participants, baiting the violence. And the UIC students, angry to the point of tears, had to be held back from making similar mistakes, until finally the protesters, facing the crowd, linked arms as they had planned, coming together in a circle.

Bernie Sanders had nothing to do with this, but Trump is responding by threatening Sanders anyway

Many of the Trump protesters in Chicago treated the rally's cancellation as a victory. Many Trump supporters, on the other hand, were outraged: Not only had the protesters not been put in their place, but they'd won.

And so many Trump supporters, now seeing themselves as the victims, tried to figure out what nefarious power was really to blame.

Some seized on ISIS — one online video claimed the protester who charged the stage in Dayton was affiliated with the terrorist group, and Trump then repeated the claim. When called out on its falsehood Sunday, he protested, "All I know is what's on the internet." (Trump is generally not known for exhibiting care in repeating internet rumors, but this one is particularly dangerous: McGraw's justification for wanting to kill Rakeem Jones in Fayetteville was that Jones "could be part of ISIS.")

But in the case of Chicago, Trump and his supporters have attributed Friday night's mishegas to the nefarious doings of the Hillary Clinton and Bernie Sanders campaigns.

There is a shred of evidence for this. But only a shred. Many of the protesters in Chicago happened to be Sanders supporters, and one clip of the venue after the rally was canceled shows a crowd of protesters chanting, "Bernie! Bernie!"

But there's a big difference between "people protested a Trump rally and some of them were Bernie Sanders fans" and "the Bernie Sanders campaign orchestrated a shutdown of a Trump rally."

There's simply no evidence to suggest the latter is the case. Both the Sanders campaign and grassroots groups associated with it have disowned any involvement in the Trump protests; in fact, the grassroots network People for Bernie wrote in a Medium post: "We strongly advise all supporters of Bernie to follow our lead and just support this [anti-Trump] movement, without trying to own it or use it to advance a candidate that SOME of us support."

It goes without saying that the facts have not stopped Donald Trump from continuing to blame the Chicago protest on Sanders. By Sunday, he was openly threatening Sanders and his supporters:

Bernie Sanders is lying when he says his disruptors aren't told to go to my events. Be careful Bernie, or my supporters will go to yours! — Donald J. Trump (@realDonaldTrump) March 13, 2016

And just as they've done for months, Trump's supporters absorbed the message Trump was trying to send.

Man. A pastor speaking at Trump's rally in Illinois just got the crowd to chant "better be careful" (to Bernie Sanders). — Daniel Dale (@ddale8) March 13, 2016

Other Republicans are finally acknowledging that what Trump is doing is unacceptable

One of the many problems facing the three non-Trump Republican presidential candidates — Ted Cruz, Marco Rubio, and John Kasich — is that as much as they want to attack Trump, they don't want to alienate his supporters. This makes it very difficult to condemn the violence at Trump rallies.

That's especially true when the violence is being directed at liberal protesters who are disrupting events — an activity that Republicans have not only condemned but linked to the "lawlessness" of protests and unrest in Ferguson, Missouri, in 2014 and Baltimore in 2015.

So when Trump's opponents were asked during the CNN debate about the violence, both Cruz and Rubio defended Trump; Kasich condemned him. After Chicago, though, there seems to have been a shift. Kasich has gotten much more strident in denouncing Trump; Rubio, too, now appears to be wavering on whether he could support Trump as the nominee.

Kasich on if he'd still support Trump as nom: "Makes it extremely difficult." When pressed, said to "take a deep breath + see where it goes" — Kailani Koenig (@kailanikm) March 12, 2016

Oh wow. Rubio looks to be the 2nd GOP contender to have his humanity broken on the wheel that is Donald Trump. https://t.co/LAEkeJvVyW — Jeff Spross (@jeffspross) March 12, 2016

Rubio, in particular, continued to dole out blame to the protesters as well as to Trump.

Ironically, after the events of this weekend, that attitude makes a little more sense than it did the first time Rubio expressed it. Because it's clear that all participants — supporters, protesters, and law enforcement — are increasingly uninterested in backing down from a confrontation.

Trump's subsequent rallies have been less eventful. But they've been tenser.

The rallies Trump has held in the days since Chicago haven't been as chaotic, and no one appears to have been assaulted. But they're still marked by dangerous situations.

There were many protesters at Trump's rally in Cleveland on Saturday. At his rally in Dayton, a protester attempted to rush the stage — an action that, given that Trump has Secret Service protection, was legitimately life-threatening. And protesters in Kansas City reported they were pepper-sprayed by police.

In other words, protesters aren't just getting more coordinated. They're getting bolder and more aggressive. And so are law enforcement officials.

The combination of the two — and what one can only assume is a commensurate response from Trump supporters — is making every Trump rally feel tense.

This tension may or may not be related to violence — after all, McGraw's assault on Jones came out of nowhere, and it doesn't appear that anyone but Jones felt threatened at the time. But it's making a lot of people feel that anything could happen at a Trump rally. And as Josh Marshall of Talking Points Memo has pointed out, that attitude often attracts the people — on both sides — who are most interested in instigating violence.

As Trump rallies get more press, tensions will grow at the next rally. As tensions grow, the odds of violence – or at least of shouting and shoving — will also grow. As more incidents happen, there will be more media coverage.

And the more all of this ratchets up, the more likely it is that the next incident will be more violent than anything we've seen. Many people, including Marshall, are worried someone will die.

It would be nice if one side unilaterally disarmed — if every liberal activist in the country, for example, simultaneously decided that the risk of getting killed at a Trump rally outweighed the benefits. But that's not going to happen, any sooner than every Trump supporter will simultaneously decide that it's enough to let the police do their jobs and every police officer decide that they don't need to put their boots on anyone's neck to keep the peace.

Trumpist violence is a threat to American democracy

Much of Donald Trump's appeal to his followers is that he throws off the yoke of "political correctness" and says the things they believe need to be said about what's wrong with America and whose fault it is — even when other people get offended.

In other words, Trump gets his power from his ability to violate norms.

But when it comes to political discourse and democratic decision-making, there are two kinds of norms. There are norms that can be questioned, or even rejected, while still participating in the process as a whole. And then there are norms that, if they're eroded, bring the whole system down with them.

Democratic societies only function because everyone agrees to behave in particular ways. Everyone agrees that (private) physical violence is an inappropriate way to settle any dispute — and that it is especially inappropriate to target people for violence based on what they say or how they vote.

Everyone agrees that law enforcement officials ought to be trusted (and trustworthy) to apprehend people who violate the law. And everyone agrees that the justice system ought to deal impartially with lawbreakers.

Except now Donald Trump is challenging those ideas — as if they were just so many more forms of "political correctness" keeping his supporters from expressing the full depth of their anger.

This isn't an overstatement. John McGraw is being charged with assault for punching a defenseless man who was already in law enforcement custody. Donald Trump is proffering — or at least saying he'd like to proffer — his immense money and power, not to mention his stature as a presidential candidate, to defend the legitimacy of McGraw's actions.

At the same time that Trump is offering protection to his supporters who engage in assault, he's threatening to use the justice system to target those who disagree with him: to start arresting and pressing charges against protesters with the aim of ruining their lives.

It's hard to tell what's more corrosive: the fact that Donald Trump, the potential 45th president of the United States, is all but promising to use the power of government to protect his followers and target his critics; or the fact that Donald Trump, the man in America most likely to get on the news, is encouraging his followers to beat up people they find obnoxious.

No one knows how far this is going to go

Trump's rallies are becoming a staging ground for these conflicts, and they'll continue to attract people who are uninterested in preserving norms against violence. But there's no way this stops at rallies.

Trump knows this, because the very first time he defended the violent "passion" of his followers it was after the August hate crime in Boston — the beating of a homeless man.

These incidents haven't been common — yet. But there's no reason they won't become more frequent after this weekend, which persuaded both Trump supporters and protesters that they were under attack. Already, a student at Wichita State is claiming that his Latino friend was punched by a man at a gas station who yelled, "Brown trash, go home, Trump will win!"

Maybe it's gone so far that even Donald Trump can't stop it. But no one knows that yet, because Donald Trump hasn't tried. He continues to take every opportunity to legitimize the things his supporters are doing in his name, and to demonize the protesters whom those supporters might be targeting.

Trump is responsible for himself, and for his followers. What has happened and what will happen is on his hands.