It’s a quiet Thursday in Tehran. Campaigning and electioneering isforbidden on election eve, and the crowds are gone, but the tension ispalpable. Here and there are still visible people wearing the ubiquitousgreen armbands that signal support for former Prime Minister Mousavi.Everyone, but everyone, has only one thing on their minds, and rumorsare flying, gossip is exchanged, and the latest news–true or not–ispassed from mouth to mouth and via cell phone and text messages. Outsidethe gigantic, concrete edifice of the Interior Ministry, which hasresponsibility for counting the votes, a pair of young women wearinggreen smiled as we passed each other. It’s inside that building,overlooked by a huge portrait of Ayatollah Khomeini, where many Iraniansworry that the vote will be stolen.

Though quiet now, over the past several days Iran has seen an outburstof political activity that far surpasses anythinge the gathering stormof the 1978-79 toppling of the Pahlavi dynasty. Last evening, I strolledacross the campus of Tehran University, Iran’s largest and mostprestigious school. In the streets outside, thousands of green-cladstudents were laughing, cheering and carrying banners, and from therooftops across the street people were throwing confetti that raineddown on the streets below. Cars and vans, flying green flags, cruisedthe streets. A small group of supporters of President Ahmadinejadmarched past, drawing jeers and mocking chants. A guard at the gate, anolder man who lost a leg in the 1980s war with Iraq, smiled approvinglyand said, of the Mousavi crowd, “It’s a revolution.”

A revolution. That’s a phrase I’ve heard over and over again in the lastfew days, from students, office workers, taxi drivers, and passersby.

In fact, it may be something less than that, since all three challengersto Ahmadinejad, including Mousavi, are establishment figures. Yetthere’s no denying the political and social movement that is buildingagainst the president, mostly around Mousavi’s brilliant campaign. Andthe contempt for Ahmadinejad is everywhere, from well-connectedobservers and analysts, government officials, and ordinary Iranians I’veencountered. A few days ago, as I headed over to Ahmadinejad’s campaignheadquarters, I stopped a man to ask directions. “Ahmadinejad! Why doyou want to go see him? He destroyed the country!” A few blocks later, awell-dressed man comes up to me, just outside the president’s governmentoffice and down an alley from the campaign headquarters. He introduceshimself as an employee in the office of the president. He says thatAhmadinejad is a fool. And he adds: “The mullahs [the Iranian clergy]are like idols. They must be broken!” He pulls down his shirt to show mea bullet wound from the war.

To counter the Mousavi green, the Ahmadinejad campaign has wrappeditself in the Iranian flag–literally. Like proper ultranationalistextremists, or perhaps like Republicans, the president’s campaign isusing Iran’s tricolor flag as its election symbol. At an Ahmadinejadrally, thousands of Iranian flags are handed out by campaign workers,and the crowd shakes the flags as if they were spears in combat. But ata competing Mousavi rally, 20,000 supporters chant: “Mousavi! Mousavi!Take back my flag!”

There’s worry and anger about cheating and unfair campaigning.Yesterday, the state-run Iranian TV gave Ahmadinejad twenty minutes offreeair time for a speech, while offering one minute each to his threerivals. (They turned it down contemptuously.) At a Mousavi rally, peoplechant: “Iranian TV has become Ahmadinejad’s PlayStation!” A man saysthat if there is evidence of cheating, people won’t stand for it. Later,the crowd chants: “If there is any cheating, we are going to make hellin Iran!” Rumors that people would storm the offices of Iranian TV ifAhmadinejad were given the free time proved unfounded, and the speechwas aired without incident.

But there’s an uneasy feeling that, especially if the vote is close, oneside or the other won’t accept the results. Perhaps the greatest dangercomes from the angry, inflamed supporters of Ahmadinejad, though ahighly informed analyst says that Iran’s Leader, Ali Khamenei, will beable to control the backers of Ahmadinejad in the event of a Mousavivictory. But there’s no question that Iran is highly divided, and whenthe results are announced–probably Saturday morning–there will be afew days of tension before it’s clear how the voters on the losing sidereact.

“I hope the gap is wide enough that the losing side accepts it,” says awell-known professor at Tehran University. If Ahmadinejad loses, if thegap is wide, Khamenei will put a lot of pressure on him not to maketrouble.”

The reality is that Khamenei and his all-powerful Council of Guardianshas approved all four candidates, and virtually everyone I’ve spokenwith says that the Leader will be happy if either Ahmadinejad or Mousaviwins. It’s even likely that Khamenei may have decided that Ahmadinejadhas served his purpose, and that a more acceptable, more moderatepresident would better serve Iran’s broader interests. “When Bush waspresident, perhaps Iran needed a barking dog to response to the barkingdog in Washington,” says one Iranian observer. “But now, with Obama,it’s different.”

Perhaps. The neoconservatives argue that, whoever wins, the rulingpowers-that-be will remain–and that’s true, as far as it goes. Butthere’s no denying that two vastly different, competing social movementshave been mobilized for this election, and that very real social forcesare at work.