What's eroding in Portland is the quality Max Weber considered essential to a functioning state: a monopoly on legitimate violence. As members of a largely anarchist movement, antifascists don't want the government to stop white supremacists from gathering. They want to do so themselves, rendering the government impotent. With help from other left-wing activists, they're already having some success at disrupting government. Demonstrators have interrupted so many city-council meetings that in February, the council met behind locked doors. In February and March, activists protesting police violence and the city's investments in the Dakota Access Pipeline hounded Mayor Ted Wheeler so persistently at his home that he took refuge in a hotel. The fateful email to parade organizers warned, "The police cannot stop us from shutting down roads."

All of this fuels the fears of Trump supporters, who suspect that liberal bastions are refusing to protect their right to free speech. Joey Gibson, a Trump supporter who organized the June 4 Portland rally, told me that his "biggest pet peeve is when mayors have police stand down ... They don't want conservatives to be coming together and speaking." To provide security at the rally, Gibson brought in a far-right militia called the Oath Keepers. In late June, James Buchal, the chair of the Multnomah County Republican Party, announced that it too would use militia members for security, because "volunteers don't feel safe on the streets of Portland."

Antifa believes it is pursuing the opposite of authoritarianism. Many of its activists oppose the very notion of a centralized state. But in the name of protecting the vulnerable, antifascists have granted themselves the authority to decide which Americans may publicly assemble and which may not. That authority rests on no democratic foundation. Unlike the politicians they revile, the men and women of antifa cannot be voted out of office. Generally, they don't even disclose their names.

Antifa's perceived legitimacy is inversely correlated with the government's. Which is why, in the Trump era, the movement is growing like never before. As the president derides and subverts liberal-democratic norms, progressives face a choice. They can recommit to the rules of fair play, and try to limit the president's corrosive effect, though they will often fail. Or they can, in revulsion or fear or righteous rage, try to deny racists and Trump supporters their political rights. From Middlebury to Berkeley to Portland, the latter approach is on the rise, especially among young people.

Revulsion, fear, and rage are understandable. But one thing is clear. The people preventing Republicans from safely assembling on the streets of Portland may consider themselves fierce opponents of the authoritarianism growing on the American right. In truth, however, they are its unlikeliest allies.