More than three months before any ballots have been cast at the Republican convention, Roger Stone, Donald Trump’s on-again, off-again consigliere, has delivered the campaign equivalent of a severed horse head to delegates who might consider denying Trump the nomination. Trump’s supporters will find you in your sleep, he merrily informed them this week. He did not mean it metaphorically.

“We will disclose the hotels and the room numbers of those delegates who are directly involved in the steal,” Stone said Monday, on Freedomain Radio. “If you’re from Pennsylvania, we’ll tell you who the culprits are. We urge you to visit their hotel and find them. You have a right to discuss this, if you voted in the Pennsylvania primary, for example, and your votes are being disallowed,” Stone said.

Over the years, I’ve covered elections in Iraq, Iran, and Burma. Stone’s taunt is every bit as threatening as anything I heard in those places, which have far less experience than America with democracy. Such is the moment we currently inhabit.

By now, we know most of the chapters in Trump’s political playbook: the epithets for “low-energy” Jeb and Lyin’ Ted and Little Marco, and the bombshell provocations—about, say, a nuclear strike in Europe—as a way to draw attention away from unfavorable news and missteps. And, throughout, of course, the mockery of women. But as we approach the growing prospect of a contested convention, in which delegates can make game-time choices about whom they will support, it’s becoming clearer that Trump may seek to shape the outcome by using his most unwieldy weapon of all: the latent power of usually peaceful people.

It’s easy to mock Trump for his thin-skinned fixation on the size of his audiences, but that misses a deeper point: you can’t have a riot without a mob. Even before he was a candidate, Trump displayed a rare gift for cultivating the dark power of a crowd. In his role as the primary advocate of the “birther” fiction, he proved himself to be a maestro of the mob mentality, capable of conducting his fans through crescendos of rage and self-pity and suspicion. Speaking to the Times editorial board, in January, he said, “You know, if it gets a little boring, if I see people starting to sort of, maybe, thinking about leaving, I can sort of tell the audience, I just say, ‘We will build the wall!,’ and they go nuts.”

The symbiotic exchange between a leader and his mob can thrive on what social psychologists call “emotional contagion,” a hot-blooded feedback loop that the science writer Maggie Koerth-Baker describes as “our tendency to unconsciously mimic the outward expression of other people’s emotions (smiles, furrowed brows, leaning forward, etc.) until, inevitably, we begin to feel what they’re feeling.”

When we are exposed to the right energy, even those of us who are not inclined to cross the boundaries from politics to force will do things that we would ordinarily consider reprehensible. Stephen David Reicher, a sociologist and psychologist at the University of St. Andrews, in Scotland, who has studied soccer mobs and race riots, told Wired last month, “People don’t lose control, but they begin to act with collective values.” Recently, he has turned his attention to studying Trump’s crowds. “It’s not your individual fate that becomes important but the fate of the group.”

And therein lies the key to Trump’s ability to introduce menace into the convention: he does not need to call upon his supporters to do anything but protect their newfound sense of identity and purpose. Stone, the political operative and self-described practitioner of “dirty tricks”—a man who (again, no metaphor) has a tattoo of Nixon on his back—has mapped out the fantasy that they will offer to their people, to explain what happens if Trump falls short of the twelve hundred and thirty-seven delegates he needs to secure the nomination. “Either Trump will have twelve hundred and thirty-seven votes, in which case the party will try to throw out some of those delegates in a naked attempt to try to steal this from Donald Trump, or he will be just short of twelve hundred and thirty-seven, in which case many of his own delegates, or, I should say, people in his delegate seats, will abandon him on the second ballot,” Stone said Monday. The convention, he has already told Trump voters, is rigged against them.

“So the fix is in,” Stone said on Monday. “If Trump does not run the table on the rest of the primaries and the caucuses, we’re looking at a very, very narrow path in which the kingmakers go all out to cheat, to steal, and to snatch this nomination from the candidate who was overwhelmingly selected by the voters, which is why I have urged Trump supporters: come to Cleveland, march on Cleveland, join us in the Forest City.”