What are Mousavi's options now?

Defying an explicit government ban to hold a rally, hundreds of thousands of Iranians stretching for miles across downtown Tehran marched to support Mir Hossein Mousavi, the moderate presidential candidate who says he is the rightful winner over incumbent Mahmoud Ahmadinejad.

Standing atop a car amid an ocean of his supporters – many of them wearing the green of the campaign – Mr.Mousavi shouted to the crowd: "God willing, we will take back our rights!"

Politically and procedurally, options are very limited for the Mousavi camp to challenge Mr. Ahmadinejad's declared 2-to-1 landslide victory in the Islamic Republic.

"They can't change anything. It's done," said a political analyst in Tehran who requested anonymity, given the current situation.

Ina bid to ease three days of street protests and violence in the capital and across the country, Iran's supreme religious leader Ayatollah Ali Khamenei on Sunday ordered the powerful Guardian Council to "carefully probe" allegations of fraud listed in a letter from Mousavi that called for results to be annulled because of fraud.

Although some Mousavi supporters might see hope in that action, experts in Tehran are skeptical that Mr. Khamenei would adjust a result. On Saturday – just a day after the vote, instead of the customary three – he sanctioned Ahmadinejad's victory, calling it a "divine assessment." [Editor's note: The original version misspelled Ayatollah Ali Khamenei's surname.]

Council chief cut from same cloth as Ahmadinejad

The powerful Guardian Council includes six clerics appointed by Khamenei, known as the supreme leader, and six jurists selected by the judiciary chief and confirmed by the parliament. Its head is Ayatollah Ahmad Jannati, a hard-line cleric cut from the same archconservative cloth as Ahmadinejad.

There is "no chance, absolutely" that the council will change the result, says the Tehran analyst. "I gather this is just something for saving face."

Mousavi has no options except for rallies like the one held on Monday, or continuing protests and rioting in the face of an escalating use by the regime of riot police, ideological militias, and vigilantes.

Monday's illegal rally marked the first public appearance for the defeated candidate since Friday's hotly contested election. Mousavi has vowed to fight for those who cast votes for him and were galvanized by their anti-Ahmadinejad views to make an unprecedented turnout of more than 80 percent.

"The vote of the people is more important than Mousavi or any other person," Mousavi said.

Mousavi followers rekindle pre-vote fervor

Footage from the demonstration showed a crowd of hundreds of thousands that stretched for several miles in central Tehran – a counterpoint to the tens of thousands who turned out on Sunday to cheer Ahmadinejad at his victory rally.

Completely outnumbered, riot police reportedly stood by,helmets off and shields lowered. But if past days are any guide, the stage was set for another round of fierce clashes into the night.

Overnight Sunday, police reportedly raided student dormitories at Tehran University, where some 3,000 students had earlier held an anti-Ahmadinejad rally. Rooms were damaged, computers smashed, and hard drives taken, and students beaten and arrested, according to the Associated Press (AP).

On Monday, AP reported that one of its photographers witnessed Iranian security forces firing at the crowd, killing one person and seriously wounding several others.

The violence has been some of the worst in a decade. But there was no question who ruled the streets on Monday, as people reportedly came out of apartments to join the throng – rekindling for a moment the self-confidence exhibited by Mousavi supporters in electrifying street demonstrations before the vote.

Editor's note: This story was updated at 3:30 p.m. on June 15.