Iran’s political crisis would end pretty quickly if the opposition went toe-to-toe with the security forces - and no matter how courageous and determined the demonstrators, the likelihood of them toppling the regime on the streets right now is pretty remote. Although at least 17 and perhaps many more opposition supporters have been killed and hundreds have been arrested, the regime has used only a fraction of its capacity for violent suppression, and its security forces show no sign of wavering or splintering. The authorities have warned that defiance of bans on demonstration will no longer be tolerated, and reports out of Iran Tuesday suggested that the regime may be moving to arrest opposition presidential candidate Mir-Hossein Mousavi. The days following the election saw more than a million people protesting in Tehran, but by Saturday that number had reportedly been reduced to 3,000, and on Monday just 1,000 were said to have made it to the demonstration. But the dwindling crowds on the streets doesn’t mean the opposition is beaten.

The authorities are showing little sign of backing down. The Guardian Council - the 12 clerics appointed to oversee elections in the Islamic Republic - announced on Tuesday that despite evidence of irregularities, there would be no annulment of the result as demanded by the opposition. Later in the day, Supreme Leader Ayatullah Ali Khamenei did order the Council to take a further five days of assessment, giving the regime time to fashion a political response to the crisis. (See pictures of Neda, the young woman who’s death has rallied the opposition.)

But Khamenei himself, the security forces and the judiciary have warned against further protests. While urging continued defiance and planning further rallies for Wednesday and Thursday, Mousavi and other opposition leaders have not yet given their followers clear marching orders. The challenge, for the opposition, is to evolve a strategy to sustain a political challenge over weeks, months, and even years in the face of a violent crackdown on street demonstrations.

The regime appears to have adopted crowd-control measures at once smarter and more brutal. Security forces and allied militia simply take control of the streets before the demonstrators do, and prevent opposition protests from achieving a critical mass by beating, tear-gassing and in some instances shooting at those trying to congregate. Still, even the limited violence unleashed thus far has created its own martyrs, such as 27-year-old Neda Agha Soltan, whose shooting death has become a rallying point for further outrage. (Read “Joe Klein: What I Saw at the Revolution.”)

The violence of the authorities puts opposition leaders in a bind: They need to maintain the momentum of their protest movement, but are aware that they’re unlikely to win on the streets, and that confrontation could bring massive bloodshed that could also kill off the prospects for near-term change. While a small hard core of more committed, younger activists may be willing to confront the security forces, the opposition movement will falter unless it is able to develop tactics that can keep hundreds of thousands of people involved, and also make skillful use of its considerable presence within the various corridors of power.

Mousavi on Sunday reiterated his supporters’ right to peaceful protest, but urged them to show restraint and declared,”I will never allow this beautiful green wave to risk its life because of me.” Acknowledging limited options available to him, he told them, “I believe your motivation and your creativity can still win your legitimate rights through civil ways.”

There has been some suggestion that the opposition might call a general strike - a form of passive resistance that does not involve directly confronting the guns of Ahmadinejad’s loyalists. There were online attempts to stage-manage the strike - for example, to go shopping but not to buy anything. While some industrial sectors such as Tehran’s bus drivers have been famously combative and willing to use the strike weapon in labor disputes, it remains to be seen whether that tactic can be effectively used as a general form of protest in an economy where so many depend on employment associated with the state, and unemployment levels are high. And general-strike calls, because of the economic risk to participants, would necessarily have to be used sparingly.

Despite fantasies of insurrection in some of the more fevered Western media assessments of the confrontation, the balance of forces appears to militate against a knockout blow by either side. U.S.-based Iran scholar Farideh Farhi, speaking to the Council on Foreign Relations, stressed that Ahmadinejad and the Supreme leader may not have the majority of the people behind them, “but they do have support. They also have the resources of the state - both financial and military. So that makes them quite robust.”

At the same time, Farhi notes, the opposition coalition includes some very powerful figures from within the regime, who together command the support of a large section of the population. Thus, she warns, “To assume that this will lead ultimately to a victory of one over the other is unrealistic as well as dangerous because it may come at the cost of tremendous violence.” More likely, she argues, is the pursuit of some sort of compromise that allows the regime to back down to some extent, without necessarily surrendering.

Such a compromise may be shaped by the battles inside the corridors of power. The clergy, whose blessings are a key source of legitimacy for the regime, is clearly divided over the government’s handling of the election and its aftermath. Much has been made of the fact that the Assembly of Experts, the 86-member clerical body that picks the Supreme Leader, also has the right to remove him from office, and there has been speculation that former President and Mousavi ally Akbar Hashemi Rafsanjani, who chairs the Assembly, has been lobbying clerics to rebuke Khamenei’s handling of the debacle. Whatever the reality, there’s little doubt that many of Iran’s senior clerics view Khamenei as having degraded the principle of a clerical Supreme Leader acting as a guide and arbiter to the regime’s factional battles. Khamenei has clearly become a partisan participant. (See TIME’s photo essay “In Tehran, Terror in Plain Clothes.”)

Rafsanjani has also called on the opposition to create a single political bloc to challenge Ahmadinejad. That move could have significant consequences in the majlis, Iran’s elected parliament. Its Speaker, Ali Larijani, is a Khamenei loyalist who has long been antagonistic to Ahmadinejad, and he appears to have hedged his bets in the present crisis. He has echoed Khamenei’s initial celebration of the election results, blaming foreign forces for some of the current turmoil; but he has also slammed Ahmadinejad’s government for attacks on students, and has backed an opposition call for an independent investigation of the election, on the grounds that the Guardian Council is biased towards Ahmadinejad.

Parliament will not be decisive, but it could be significant in any longer term strategy of an opposition movement that claims the mantle of the Islamic Revolution. It must approve the president’s budget, and it has the power to impeach him. It must also approve and can dismiss cabinet ministers - as Ahmadinejad discovered in 2005, when the legislature rejected his first three nominees for oil minister, and again late last year when it fired his Interior Minister for faking a degree from Oxford University.

Currently, Ahmadinejad’s own coalition controls 117 of the 290 seats in the majlis, while the reformists control 46 and pragmatic conservatives aligned with Rafsanjani and Mousavi have 53. Five seats are reserved for religious minorities, and 69 are in the hands of independents, among whom the opposition will presumably be lobbying hard for support against the president.

Whatever happens in the streets in the coming days, the opposition to Ahmadinejad, which has one foot deep inside the regime and the other in civil society, may be girding for a long-term campaign against the president’s power grab. The end result is likely to be some form of compromise between what remain factions of the same regime - albeit factions with increasingly catastrophic differences. But the question that will be in play in the weeks and months ahead is which side will have to give up more.

Tags: Ali Khamenei, Annulment, Ayatullah, Clerics, Defiance, Demonstrators, Followers, Guardian Council, Hossein, Irregularities, Judiciary, Opposition Leaders, Opposition Supporters, Political Crisis, Political Response, Presidential Candidate, Rallies, Security Forces, Supreme Leader, Violent Suppression