WASHINGTON -- The most serious challenge that Iran's Islamic rulers have faced in their 30 years in power caught President Obama and many European leaders by surprise. Their intelligence agencies did little to prepare them for a national catharsis that now pits a combustible mixture of youthful, idealistic protesters and older political opportunists against Ayatollah Ali Khamenei.

By threatening and then delivering repression blessed by his religious authority, Khamenei has turned an election dispute into a crisis of legitimacy for a regime that claims to be divinely inspired. Obama's decision to stay out of the limelight in responding to the protests is paying off in the sense of keeping the focus on those who cheat and maim Iranians.

But the president and his advisers still have not adjusted policies and tactics being overtaken by events. This is clear both from the initial "caught in the headlights" reaction by Obama as he temporized -- albeit with steely skill -- and from accounts of diplomatic and other official sources here.

The administration's own words suggest that Obama is trapped in a political version of the theory of relativity -- that he moves along a predetermined course that prevents him from seeing the new situation exactly as it occurs. He clings to pre-election ideas and assumptions, acting above all to keep alive the chances for a nuclear deal with any government that sits in Tehran.

Focusing now on obtaining the highly improbable nuclear accord neglects the moral and historical dimensions of mass protest in authoritarian societies that are now vulnerable to new communications technology. Such moments release a moral energy in once-submissive populations that rulers must crush, accommodate or yield to. Whatever their ultimate choice -- crushing is clearly the initial one -- the ayatollahs will never be the same.

This is not to underestimate the difficulties Obama faces, as do John McCain and other critics who accuse the president of passively accepting what Iranian dissidents rightly call President Mahmoud Ahmadinejad's "coup."

But Obama should not have blurted out the (accurate) observation that challenger Mir Hossein Mousavi would probably not change Ahmadinejad's foreign and nuclear policies. This is the kind of assessment that intelligence chiefs whisper to their bosses to explain that their missed call doesn't really matter much.

Yes, Mousavi is a man of the Islamic establishment who has brutally put down dissent himself and something of an opportunist. But if he, and his clerical allies, were unexpectedly to overcome both Ahmadinejad's coup and Khamenei's crackdown, those who have been in the streets would hold the new government to different, higher standards of governance and engagement with the world. Mousavi might well disappoint them. But he would then have to deal with this newly politicized population.

Judged by what they have -- and have not -- said publicly, administration policymakers seem to underestimate the sense of empowerment that the demonstrations inevitably create for the protesters, especially among the young.

The experience of witnessing three very different citizens' uprisings in the 1980s leads me to that expectation. I saw the "people power" movement sweep aside the Marcos regime in Manila, and Solidarity emerge from nothing to whittle away Polish communist rule and the Soviet empire. The euphoria of empowerment can also quickly turn to horror, as it did in Beijing's Tiananmen Square in 1989.

But what remains -- even from Tiananmen -- are the scenes of heroism, and the acknowledgement of a population's common humanity that rises from revolts for more dignity and freedom. To see a Chinese worker throw his bicycle -- a necessary and relatively expensive possession in that day -- beneath a military truck to block troops from attacking students is unforgettable. So is witnessing a parade by diplomats from the Chinese Foreign Ministry supporting the demonstrations.

And if I have not forgotten it, neither have the Chinese people. They were changed by these events, even if their cause was suppressed by their communist rulers -- and then dishonored by the acquiescence of the first Bush administration in Deng Xiaoping's actions.

Morality as a factor in foreign policy has taken a beating recently, due in part to George W. Bush's sanctimonious exploitation of it. But ignoring its place altogether is also a mistake. Yes, it is not the American president's prerogative to meddle in Iran's protests. But neither should he prejudge or minimize the sacrifices that Iranian protesters choose to make in hopes of a better life.