Strategypage notes that people power revolts rely on a regime too reluctant to unleash the forces of the security apparatus on the people--either from moral sensibilities or fear the guys with guns won't shoot at the people if ordered to do so. And the Iranian regime is more than happy to kill and has the killers reliable enough to do the job:
While the Islamic conservatives in Iran have the support of, at most, a third of the population, they do have over a hundred thousand armed men who are willing to kill to keep their religious leaders in power. ...
The old school defenders of the Islamic tyrants in Iran appear ready to carry out some sustained killings to keep their masters in power.
We can't count on a clean revolt to rid us of this problem. And if we do, there will be a Tiananmen Square-style bloodbath as hopeful dissidents are slaughtered by the imported bully boys the mullahs rely on to keep their regime in power.
I hope instead we've been courting key military units to turn on the regime loyalists and march on the palace with our support. If not, then an aerial campaign to set back Iran's nuclear drive will be the only option other than just accepting Iran as a nuclear power.
UPDATE: TM Lutas gently chides me (and Strategypage) for not citing the basis of saying the Basij are loyal killers. It's a fair cop. I did search for a bit to find my source for importing loyal Islamists to staff the Basij but could not find it. So I went from memory. All I could find in my site with five more minutes of searching was an unlinked reference from a couple years ago:
Were I calling the shots (to be fair, really easy for me to say from my desk), I’d be pushing for a takeover by the Iranian military in the new year, with help from American forces during the rotation of forces in Iraq. US forces could move in to secure nuclear and other WMD sites and to back up the Iranian military. I read that the polls are good for us in Iran. I read that elements of the military are favorably disposed toward us. I read that the mullahs don’t trust the regular military and don’t really trust the Pasdaran—what might be considered analogous to Saddam’s Republican Guards as far as trust is concerned. Instead, like Saddam with his Fedayeen, the mullahs have imported foreigners to man the Basij paramilitaries to terrorize dissidents.
And let me add a link to a 2002 report that doesn't back up the imported part, but does state that the Basij are considered the loyal enforcers:
Due to its zeal, the Basij is often employed – with special Revolutionary Guards units – when it is believed necessary to use extreme measures to repress dissent or protest. According to some estimates, there are some 90,000 armed men in Basij militia.
There are also about a million in reserve. My guess is that imported zealots would naturally be in the active component.
I stand by my assumption that any revolt to topple the mullahs will require organized military forces if it is to win. That could be American or Iranian regular or even some Pasdaran (Revolutionary Guards). Anything else is likely to just be a regime-ordered massacre. And don't even think the vaunted international community will do anything or even care.