At this time, there is little for the US to do, that it is not already doing. The current nuclear confrontation with the US is holding back the Revolutionary Council in manpower terms. The need to guard the various nuclear refinery sites, and to mitigate an air strike on the sites, prevents the Revolutionary Guards from moving these guards to Tehran to help with the crackdown. The manpower shortage of the IRGC allows the students to continue protests. The on-going economic embargo and maritime interdictions similarly limit the ability of the IRGC to operate against the students. Therefore, it is vital that we continue our peacetime confrontations and containment against Iran.
I will re-iterate my call for an American Embassy in Tehran, though. Such a move will head off the Hardliners' characterizing the protests as an American conspiracy.
Similarly, the US should refrain from material support of the student protests, other than refugee protection. There is plenty of light weapons in Iraq, should the protesters take up arms. And the Israeli Mossad is likely already aiding the insurgency.
Right now, the IRGC is being pulled in multiple directions. It has to continue supporting Hezbollah and possibly Hamas by sending out weapon shipments. Following the terrorist attack in Eastern Iran, IRGC has to step up security across the Persian empire to confront the ethnic separatists. The ongoing nuclear crisis means that they have to maintain the security posture at the nuclear sites. The possibility of an air strike means that all of the IRGC air defense sites (in addition to the Air Force air defense sites) need full manning. American stealth bombers and Israeli cruise missiles means the listening sites (where people listen for jet and missile sounds) need full manning, too. And they have to deal with the student insurgency. The IRGC is running out of people.
The Revolutionary Council is politically constrained, as well. Most of the college students are the sons and daughters of Iran's middle and upper class, many of whom working in the government bureaucracy. If the Revolutionary Council starts shooting protesters indiscriminately, they are bound to kill the children of senior government workers. Such a move would turn the bureaucracy, the machinery of governance, against them. In addition, the military has not taken a side in this insurgency. The military has to uphold the Iranian regime, but the children of the senior officers are marching in the streets. The council cannot afford to alienate the military.
So the status quo is leading toward a regime change in Iran. If the students keep on protesting, the protests will highlight the political constraints of the council, its limitations. The Revolutionary Council, like all totalitarian regimes, operates on the perception of its omniscience and omnipotence. People report on their neighbors because they are afraid of the reach of the secret police. If the Iranians find out that the IRGC has political limits, they will be less likely to report their neighbors and more likely to keep on testing the behavioral limits. The ethnic separatists will operate more openly. The black marketeers will be more brazen in hawking their wares. The decline of social controls will bring about more social disruptions. The protests will get closer and closer to the government buildings. At some point, the IRGC will have a showdown with the protesters, trying to restore its perception of control. If the students succeeds in embarassing the IRGC, that's when regime change will take place.
The critical question for the US and the West concerns Iran's nuclear program. If a revolution occurs, hopefully the nuclear program stays above the fray, and enters a conservatorship awaiting a legitimate government. A renegade IRGC commander may transfer nuclear material to a terrorist organization, although that possibility is slim due to the bureaucratic nature of a government entity like the IRGC. The military may take over the nuclear program during the revolution because it is a vital strategic bargaining chip for Iran as a state.
The nature of the student revolution remains unclear, because students operate on emotion. The last student revolution in Iran led to the current theocratic regime. The students today coalesced around the opposition to government oppression, but there is likely much disagreement on the endstate, of the revolution. Various politicians are trying to hijack the movement, with Mousavi and Rafsanjani being possible examples. A hijack is possible if a politician can bring a bureaucratic entity or a guild (the merchant or clerical guild, say) into the protest movement. This politician can ride the resulting goodwill all the way to the top. We will hear his name as soon as the IRGC kidnaps him.
Ideally, this revolution would lead to a new constitutional convention to re-write the constitution. This is a likely outcome because of the neutrality of the military and the government bureaucracy in general, so far. These entities serve as moderating influences on both the Revolutionary Council and the students, barring further radicalization and escalation. As neutral actors, they have the authority to strike a bargain, hopefully allowing the clergy to save face and take on a lesser role. Their governmental nature make them invested in the current form of government and resistent to radical changes. Minimizing change would minimize social upheavals and human suffering.
However, if the IRGC escalates by massacring protesters, Marxist-type revolutionaries will have more followers among the students. The radicalization of the movement will lead to a post-revolution purge we've seen in France, Russia, China, and elsewhere. A violent revolution would be inevitable.
Factions of the IRGC may, in self-preservation, stage a coup against the Revolutionary Council. Such a move would allow the IRGC to bargain with the military and the rest of the government in the resulting transitional governance, over its future roles. This action would also preserve the income and fiefdom of much of the IRGC bureaucracy, while sacrificing few offenders to appease the students. For the IRGC, this is the most favorable outcome in a regime change, thus highly likely to occur. The Revolutionary Council may anticipate this and counter-move by purging the IRGC, but that would weaken their protection and force the Council to accept a compromise with the students.
Given that we in the public rarely hear about the bureaucratic machinations in Iran, it is unlikely for us to confirm any of these scenario until the last moment. For everyone's sake, I hope the Revolutionary Council compromises with the students through a constitutional convention, but there are too many entrenched interests in the IRGC to hope otherwise. The IRGC will probably survive in some form in the end, hopefully with more checks on its power. For the US we need to keep up the war rhetoric and nuclear confrontation all the way to the end, but ready to detente at the earliest opportunity.