How ironic. A regime that came to power through a brutal revolution, in a country suspected of secretly developing a nuclear weapon, is now facing its biggest challenge from peaceful civil disobedience.

The street demonstrations by day and haunting chants echoing across rooftops by night are not — so far — a counterrevolution.

That's not even their intention. What they are doing, however, is forcing Iran's Islamic regime to face the same ideals that have swept across five continents over the last quarter of a century — the supremacy of popular will, justice, accountability and the transparency of power.

The demonstrators may not succeed. Iran's "New Right" — the war-hardened second generation of leaders, who wear hats instead of turbans — still has the political power and the physical tools to contain the current confrontation.

But long term, the feisty election campaign and the postelection protests have given legitimacy to the core ideas of political change. It's all central to what the United States wants to see happen throughout the Middle East. Yet it's also so Iranian.

For 14 centuries, Shiism has been about passionate belief, about sacrifices in the name of perceived injustice and challenges to leadership. These are the principles that stirred people to action when questionable results were announced just two hours after the polls closed.

For a century, Iranians have been political trailblazers in the 57-nation Islamic bloc. During the 1905-1911 Constitutional Revolution, a powerful coalition of intelligentsia, bazaar merchants and clergy forced the Qajar dynasty to accept a constitution and Iran's first parliament. In 1953, the democratically elected National Front coalition of four parties led by Prime Minister Mohammed Mossadegh pushed constitutional democracy and forced the last Pahlavi shah to flee to Rome — until U.S. and British intelligence orchestrated a coup that put him back on the Peacock Throne. And in 1979, yet another coalition of bazaaris, clergy and intellectuals mobilized the streets to end dynastic rule that had prevailed for about 2,500 years.

So the angry energy unleashed last week from the northern Caspian coast to southern Shiraz is the natural sequel, spurred on by 21st-century technology and the Internet. Each of the first three phases left indelible imprints on Iranian politics. The fourth will, too.

But the current green-swathed uprising involves an emerging coalition that includes students and sanctions-strapped businessmen, taxi drivers and former presidents, civil servants and members of the national soccer team.

Senior clerics in the holy city of Qom, many of whom never favored an Islamic republic for fear its flaws would taint Islam, also have not embraced the election outcome. Even the brother of Supreme Leader Ayatollah Ali Khamenei, Hadi Khamenei, himself a cleric and former member of parliament, urged that an impartial committee investigate the election results and provide a full public accounting. As the coalition expands, the stakes are widening well beyond who ends up as president.

Unless Khamenei can satisfy the protesters, all the brutal tools of 150,000 Revolutionary Guards and 300,000 paramilitary Basij will be unable to sustain his legitimacy.

At the same time, however, hundreds of thousands of Iranians have taken to the streets not to reject the current constitution but rather to demand that the individual rights it guarantees are enforced.

The movement already has invoked Shiite symbolism. Mourning traditionally is marked in commemorations on the third, seventh and 40th days after a death, a cycle also used to galvanize greater public outrage when the shah's forces killed protesters in 1978. The commemorations often led to new clashes and more deaths — and then volatile new cycles of mourning.

The stunning protests in this fourth phase of Iran's centurylong political journey will change the country further. The only question is how long it will take.