Some observers see Iran's courageous protests against a stolen election as a replay of the 1979 revolution that ended the tyranny of the Shah - or of the "velvet revolutions" that ended communism in Eastern Europe. Others fear a repeat of China's 1989 Tiananmen Square massacre. But none of these comparisons easily fits the unique combination of discord on the streets and infighting in the corridors of power currently under way in Tehran.

The situation is all the more dangerous and unpredictable because the election and its aftermath appears to have surprised all the major players, forcing them to improvise their responses to a fast-changing situation. President Mahmoud Ahmadinejad and Supreme Leader Ayatullah Ali Khamenei appear to have been taken aback by the surge in support for the pragmatic conservative candidate Mir-Hossein Mousavi. The decision to hastily announce what many say was an improbable landslide victory for Ahmadinejad touched off an unprecedented wave of protests that have rocked Khamenei, who has since backtracked by ordering an investigation into claims of voter fraud. Despite violent attacks on demonstrators and arrests of political figures, security forces have in the main refrained from unleashing their repressive might on the demonstrators who are openly defying the law. The partial recount of the vote has bought Khamenei time, but the crisis of legitimacy facing those in power grows by the day.(See pictures of Iran's presidential election and its turbulent aftermath.)

Violence and the threat of violence has not deterred the demonstrators, and Mousavi is showing no inclination to back down just yet. Khamenei appears to be scrambling for a compromise that will persuade Mousavi to end the demonstrations while keeping Ahmadinejad in the presidency. But the outcome of the battle of wills may depend on how the key players read the balance of forces on the street and in the councils of the regime. The situation is delicately poised; what follows are four scenarios that could resolve it.

One: Revolution 2.0?
Despite the Twitter-enabled street scenes and revived slogans of Ayatullah Ruhollah Khomeini's 1979 revolution, a repeat of that successful insurrection remains highly improbable. For one thing, the protest movement is being led by a faction of the Islamic Republic's political establishment, whose members stand to lose a great deal if the regime is brought down and, thus, have to calibrate their dissent. More important, an unarmed popular movement can topple an authoritarian regime only if the security forces switch sides or stay neutral. But Iran's key security forces - the Élite Revolutionary Guards Corps and the Basij militia - are bastions of support for Ahmadinejad. And they have hardly used a fraction of their repressive power. Also, while the opposition draws far larger crowds, there are still millions of Iranians strongly backing Ahmadinejad. So even if the government is unable to destroy the opposition, it's unlikely that the opposition will be in a position to destroy the government. (See pictures of the enduring influence of Ayatullah Khomeini.)

Two: A Tehran Tiananmen?
The harsh language used by Ahmadinejad and the Revolutionary Guards to describe opposition protests - and their invoking of the specter of an Eastern European–style "velvet revolution" backed by the West - appeared to be generating a narrative that would justify a bloody crackdown, a massive use of military force that would terrify the opposition into submission. Clearly, the limited violence unleashed by the Ahmadinejad camp thus far has failed to intimidate Mousavi and his supporters. But while it would almost certainly clear the streets, the "nuclear option" of a Tiananmen Square–style crackdown would be a potentially fatal wound to the regime's own sources of legitimacy - its limited but lively democracy and the backing of Shi'ite clergy. Discord among the mullahs is growing, with some senior clerics like the esteemed house-arrested dissident Ayatullah Hossein-Ali Montazeri publicly condemning Khamenei's handling of the election and warning ordinary soldiers and police officers that they would "answer to God" for any violence against the people. A crackdown would risk reducing a regime built on clerical authority and "managed" democracy to a tyranny on par with the Shah. Khamenei will be reluctant to go that route. But his handling of the political crisis thus far will have deepened long-standing skepticism within the clergy about his abilities as Supreme Leader. A harsh crackdown, even if followed by reforms, would solve an immediate crisis, but at the cost of inflicting a possibly fatal long-term wound on the regime.

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