Donald Trump's rallies have a violence problem. But it's not a matter of fringe incidents or unwelcome hooligans tarnishing Trump's image. It's a problem that starts with Trump himself, that's been going on for a while, and that's getting worse.

For the majority of Americans who are not Donald Trump supporters, the idea of a leading political candidate inciting violence against protesters — and being cheered for it — seems shocking. Where did this embrace of mob violence come from? Why does it seem that many of Trump's supporters not only tolerate but welcome and embrace his rhetoric?

It's another version of the same question many Americans have been asking for the past year: How is this happening in the United States?

Much of the answer can be found in academic research into political behavior that political scientists refer to as authoritarianism. According to this theory, authoritarians are a group of voters who prize order and conformity, and feel deeply threatened by social change, influxes of outsiders, and hierarchies being upended. When threatened, authoritarians support strongman leaders who promise drastic, decisive action to cast out outsiders and restore order.

This theory goes a long way to explaining what's happening at these rallies: The protesters whom Trump is encouraging his supporters to attack are walking, talking manifestations of the kinds of social change that Trump supporters fear. Fomenting and supporting violence against the protesters is a way for Trump to show authoritarian voters that he can be the kind of leader they crave.

This theory's implications might help explain what's happening with the violence and incitement at Trump rallies, but they also offer a warning: That violent atmosphere isn't an unintended offshoot of Trump's rhetoric, but rather it appears likely to be core to his appeal and to the motivations and desires of his support base. That suggests that this week's violence may not be an aberration but rather a harbinger.

Authoritarianism and Trumpism

This violence has held national attention since last week, when a Trump supporter named John McGraw punched 26-year-old protester Rakeem Jones in the face — and then told the press that if he saw Jones again, "we might have to kill him" because "[w]e don’t know who he is. He might be with a terrorist organization." A few days later, a Trump rally in Chicago was canceled after Trump supporters clashed with protesters at a packed arena.

Trump himself has actively, specifically encouraged his supporters to attack protesters, even going so far as to promise to pay their legal fees. And on Sunday morning, Trump sent a tweet that can only reasonably be read as a threat that his supporters will beat up Bernie Sanders supporters if there are more protests at his events:

@realDonaldTrump Send them. They deserve to see what an honest politician sounds like. — Millennials 4 Bernie (@Bernlennials) March 13, 2016

This wasn't the first time. At an Iowa event back in early February, Trump expressly exhorted his supporters to be violent toward protesters, telling them that "if you see somebody getting ready to throw a tomato," they should "knock the crap out of them." He also promised to pay the legal fees of anyone who did so: "Just knock the hell — I promise you, I will pay for the legal fees. I promise, I promise. It won’t be so much ’cause the courts agree with us too."

So what's going on here? As I've written previously, a key insight into Trump's success is that many — though by no means all — of his supporters score high for a psychological profile that political scientists call "authoritarians."

Political scientists have found that these authoritarians are highly susceptible to feeling threatened, and to reacting to those threats by desiring violent responses — all in ways that line up very clearly with what we've seen at Trump's rallies.

Authoritarians, as political scientists use the term, prioritize social order and hierarchies, which bring a sense of control to a chaotic world. Challenges to that order — diversity, influx of outsiders, breakdown of the old order — are experienced as personally threatening because they risk upending the status quo order that authoritarians equate with basic security.

Often that tendency is latent. But at times when the country is experiencing great social change or significant threats from foreigners or other outsiders, authoritarian voters become "activated": They seek a strongman leader who promises to do whatever it takes to protect them from the disorder and danger they perceive.

They gravitate toward leaders who promise to target "out-groups," such as immigrants or minorities, telling their supporters that this out-group is responsible for the threats they perceive and promising to take decisive action to remove or suppress that threat.

Authoritarians who fear terrorism, for example, might thus gravitate toward strongmen leaders who demonize Muslims, because this leader then has a means by which to explain their fear ("you are at risk from a vast and terrifying enemy whom no one else will confront") and to promise reprieve from that fear ("we'll ban all Muslim foreigners and restore an America free of people who look different").

When authoritarian voters become activated, as NYU professor Jonathan Haidt has written, it's as if a button is pushed that says, "In case of moral threat, lock down the borders, kick out those who are different, and punish those who are morally deviant."

Vox's polling supported that theory, and seemed to demonstrate that authoritarianism helps explain not just Trump's rise but why his extreme policies and rhetoric were proving so popular. Voters who scored high on authoritarianism were especially likely to be worried about the presence of Muslims and undocumented immigrants in the country, and were more likely to support sacrificing civil liberties in order to prevent terrorist attacks and the use of force rather than diplomacy in foreign policy.

How authoritarianism explains the violence at Trump's rallies

If authoritarianism can help explain what's happening with Trump's campaign on a macro scale, then it is even more powerful in helping to explain what's happening at his rallies — which are, in some ways, a microcosm of how authoritarianism works.

It's important to remember that authoritarianism is, in part, about people reacting to fears and to perceived threats. And the protesters at Trump rallies, viewed from an authoritarian's worldview, are something like a live human manifestation of those fears.

According to the LA Times, the protesters included young Muslim women in headscarves, members of the Black Lives Matter movement, and members of the Fearless Undocumented Alliance, which advocates for the rights of unauthorized immigrants in the US. In other words, all representatives of what authoritarians would (probably subconsciously) consider to be threatening out-groups and the forces of frightening social change.

When authoritarians worry about the ways this country is changing, and the outsiders who could alter their communities, they probably picture people who look a lot like those protesters. Therefore, authoritarians see the protesters as not just hecklers, but as representatives of a much larger and terrifying threat to the world as they know it. They represent the status quo order to the world that they feel evaporating beneath their feet.

The study of authoritarianism tell us that authoritarians will respond to this perceived threat by desiring a strongman leader who will promise a heavy-handed response — not out of a love of a violence per se, but rather out of a fear-based desire to reimpose order, and a belief that violence is necessary to equal the threat.

So when Trump implicitly condones or even encourages violence in response to the protesters, what authoritarians hear is something like a reassuring promise: I understand the scale of the threats that no one else sees, and I alone have the strength to do what is necessary to put down that threat. This is, after all, the same promise Trump makes when he says he will wall up the border or conduct mass deportations.

Viewed through this research, it's not surprising that a small minority of Trump supporters responded to the protests with violence. But it also explains why Trump is actively encouraging that violence: It is an obvious way to show his authoritarian supporters that he is the kind of leader they crave. And, indeed, he is.

Trump, authoritarianism, and violence

There is reason to believe that the problem will not necessarily be limited to Trump's rallies themselves: Back in August, two Trump supporters allegedly beat a sleeping homeless man with a metal pole because they believed he was Hispanic. One of the suspects apparently told the police, "Donald Trump was right, these illegals need to be deported." They were on their way home from a baseball game, not a Trump rally.

And we shouldn't expect it to get better anytime soon, because this phenomenon is driven by the desires of authoritarian voters as much as by Trump himself. A different politician with a different support base might seek to stop his supporters from attacking people. But for Trump, this presents an opportunity to show his authoritarian supporters that he is the real deal.

Trump isn't a politician; he has no track record of delivering on the promises he's making on the campaign trail. He's never built a wall, never banned Muslims from the United States, never cowed the government of Russia or China with his superior negotiating skills. But this violence gives him an opportunity to show his commitment to following through his fiery rhetoric.

That's what he's really saying when he promises to pay the legal fees of anyone who attacks protesters at his rallies: "We're under threat. I'll do whatever it takes to deal with that threat, whether it's legal or not. And if you do the same thing, I'll have your back."

That's what authoritarian voters want to hear. It makes them feel safer. But in reality, it makes all of us — Trump supporters included, given the unpredictability of mob violence — less safe.