Trump supporter Roger Stone says trouble is brewing in Cleveland if Trump falls short of the 1,237-delegate threshold to win the Republican nomination. In fact, he’s outright advocating that his supporters respond with thuggish tactics. Last week he warned, “We will disclose the hotels and the room numbers of those delegates [in Cleveland] who are directly involved in the steal. 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.”

If that seems like an empty threat, consider this. As The New Yorker’s Evan Osnos explains, “you can’t have a riot without a mob.” And if anyone knows how to exploit a constituency’s anger, it’s Trump. Writes Osnos, “Even before he was a candidate, Trump displayed a rare gift for cultivating the dark power of a crowd. … 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.’”

This is even more concerning because the prospect of a contested convention is growing. Case in point: It was a good weekend for Ted Cruz. The Denver Post reports, “The Texas senator won all 34 delegates awarded in Colorado in what amounts to a stunning rebuke of Republican front-runner Donald Trump. Cruz completed the sweep by winning all 13 delegates at the state convention in Colorado Springs.” Meanwhile, in Indiana, it’s possible not a single one of the 27 delegates headed to Cleveland will back Trump.

Trump says the GOP is “trying to subvert the movement” by using “crooked shenanigans.” And his new delegate manager, Paul Manafort, claims, “You go to these county conventions, and you see the tactics, Gestapo tactics, the scorched-earth tactics.” Two things. First, it’s Trump, not Cruz, who has benefited most from the system. Trump has won 37% of the vote so far, but 45% of the delegates. Second, the Trump campaign could have avoided this setback by doing a little homework on how Colorado delegates are allocated. The rules aren’t new; it’s just that nobody (except the Cruz camp) has been paying attention.