This current round of protests, by all accounts, are bound by none of these constraints. They reportedly began as a hard-line assault on Mr. Rouhani but quickly acquired an independent momentum and spontaneously spread. There are no leaders to imprison or publicly humiliate, no democratic agenda to tar by association with Western values and no reason for protesters to avoid disruptive tactics or slogans that antagonize the entire ruling system. These demonstrations don’t pit elites against one another but citizens against the state. Some of the people I know who were active in the 2009 uprising profess to be frightened today — of chaos and the potential for destructive demagogy. Others call for unity in opposition.

If there is one thing Americans should know by now about Iran, it is how little we know it. The Iranian regime, with its heavy-handed censorship and self-isolation, has made sure of this. So has the pitched battle over American foreign policy on Iran, which renders Iran’s domestic realities as talking points in a conversation that is really about us. There is an almost embarrassing cone of silence around today’s protesters. They live in provincial cities, Tehran reformists don’t speak for them and they are not the sorts of people connected with the domestic or international news media. Moreover, their likely demographic has been subject to casual generalizations that turn out to be wrong.

For instance, the conventional wisdom inside and outside Iran has long held that the lower and working classes in Iran were clients of the state and the core hard-line constituency. Kevan Harris, a sociologist at the University of California, Los Angeles, conducted a study of welfare recipients and political affiliation that called this assumption into question. It turns out that loyalty is not so easily bought. Welfare recipients are not more politically predictable than other Iranians. And now it seems that when members of this cohort turn up on Iran’s streets, after years of being told that there is nothing wrong with an economy that can’t keep factory doors open or food on the table, their slogans are more radical than those of the presumptive middle class.

Ayatollah Khamenei, for his part, has spent these days of rage composing anti-American tweets, warning of an American plot to dismember the country and comparing President Trump unfavorably with Ronald Reagan. This is both deflection and political savvy. Nationalism is a powerful current in Iranian life, and Mr. Trump is offering Ayatollah Khamenei the gift of a credible straw man — with alacrity, it seems. But American sound and fury mainly serve to obfuscate a domestic quandary.

Every decade or so in Iran, protests erupt whose scale, intensity and persistence make global headlines. The ideological punditry flows. We read that the regime is universally hated and about to fall, and then we read that the regime is strong and the oppositionists are marginal people of no account — because, in 2009, they were predominantly middle class, or because, in 2018, they are not. Security forces crack down, the regime doesn’t fall, and dissent remains stalwart and pervasive.

A political scientist once told me that Iran is the exception that proves the rule: It’s the textbook example of the country that meets every precondition for democratic transition but still refuses to change.

Iranian protests repeatedly come down to one thing: the accountability of the regime to its people. But Ayatollah Khamenei has buttered his bread on the other side. His power depends on the continued stranglehold of the security state, which he has also made the country’s economic center of gravity. So long as this is true, he can’t or won’t address the root cause of Iran’s chronic unrest.