Where next? That's what everyone from the tweeters and youth organisers credited with mobilising Egypt's revolution, to the King of Bahrain and Colonel Gaddafi, is asking.
Who, just a few weeks ago, would have predicted protests on the streets of Manama or Tripoli? Yet, even if 2011 turns out to be the Middle East's answer to Europe in 1848, can we imagine the dominoes from Tunisia and Egypt tipping into Iran? Can we really see Ayatollah Ali Khamenei climbing into a helicopter and being airlifted off to exile? (Where, Brazil?) Can we imagine the jubilant crowds on Valiasr Street, the doors of the political cells in Evin prison flung open and Iran's women stamping on their chadors?
The ferocity of the crackdown on street demonstrations in Tehran this week (as well as the frenzy of executions under way in the jails) are signs of a regime with a terrifying will to cling to power. But they are also signs of the regime's weakness. Divided and out of touch, it was caught unawares by the scale of protests, failing to anticipate that Mubarak's overthrow would be hailed, not as a mirror of the 1979 Islamic revolution, but of Iran's "green" uprising of June 2009. President Mahmoud Ahmadinejad was so confident Egypt was on the brink of Islamic revolution that he said it was surely the work of the Twelfth Imam (a messianic Shia figure he believes in).
The opposition movement, on the other hand, has been hugely reinvigorated. And the shot in the arm from Egypt and Tunisia taps into a climate of growing anger over economic conditions in Iran. Shirin Ebadi, Iran's only Nobel Peace Prize laureate, has refused to accept the death of Iran's opposition movement despite evidence that it has been beaten into submission. "There is fire beneath the ashes," she told me last June. Just weeks earlier in Tehran, I'd found a mood of utter despondency. Yes, change will come, young people said, but it will be too late for us. Faced with the might of the state security apparatus, the movement's leaders had pulled back. And faced with Orwellian televised show trials, mass jail-rapes, torture and hangings, most people just wanted to get on with their private lives, or get out.
Yet, it was significant that what started as anger over a fraudulent election result, had, a year later, evolved into the demand for a different form of rule. Iran was never politically sclerotic like Egypt or Tunisia. For 30 years it has had different and competing centres of power, elements of secular government, a religious hierarchy and mediating forces between them. But it also has interest groups like merchants or students and until recently a credible judiciary. Criticising the political class is routine, mocking Ahmadinejad a national sport. What was never possible before June 2009 was to attack the name of the supreme leader, guardian of the revolution, or to question the Islamic system.
But the shocking repression of 2009 changed that. People stopped believing it was possible for the rule of law to operate within a reformed Islamic republic. Many came to realise that their state was not even a conservative theocracy any more, it was a corrupt militaristic dictatorship cloaked in religion, no different from any other tyranny. That's when the graffiti in the Tehran underground began mocking Khamenei, a sure sign that, as Abbas Milani, professor of Iranian studies at Stanford University, puts it: "Inside people's heads" a profound democratic revolution has already taken place.
Yesterday, it was reported that one of the two main opposition leaders, Mehdi Karroubi, has said he is prepared to "pay any price". Are enough ordinary Iranians also ready for such sacrifice? In Ryszard Kapuscinski's seminal account of the 1979 revolution, Shah of Shahs, he describes how the people's exhaustion with despotism gave way to the moment when the nation's patience snapped and fear evaporated. In Cairo last week, the moment when the citizens stopped believing the soldiers would fire on them is now identified as the turning point.
But the Egyptian model is not easy to transpose to Iran. Yes, there is a huge young population and their internet activism has kept the ashes warm, but Iran remains isolated. The propagandists in the state media are relentless, and in rural areas people don't have satellite TV, never mind Twitter or Facebook. Even for the millions of urban, middle-class Iranians who watched the Arab revolutions live on BBC Persian until it was jammed, there is also a deep-seated fear that revolutions can bring worse rulers than those they oust. Those who remember 1979 recall how secular forces were swamped by Khomeini and the clerics. Nor do Iran's reformists have any great faith that Western powers (who toppled an Iranian democracy in 1953) won't do a Libya-type deal with the regime over its nuclear programme. In some ways, everyone in Iran, and not just the rulers, has an aversion to risking the status quo.
Perhaps the biggest factor is the military. Egypt's army is drawn from conscripts. The 120,000-strong Iranian Republican Guards and the 10 million part-time militias, the Basiji, that they control, are separate from the regular army. To say they have a vested interest in preventing revolution is an understatement. They control most of the economy. The idea that they would stand aside for a peaceful transition to democracy is fanciful.
The Islamic regime will not be able to filter the internet and jam the BBC forever and the pressure cooker will, sooner or later, blow its lid. Unfortunately, this is a revolution that won't be bloodless when it happens.