TEHRAN // Is the green wave of support for Mir Hossein Mousavi strong enough to effect a big change and leave Iran bidding farewell to Mahmoud Ahmadinejad tomorrow? Analysts and pro-reform politicians in Tehran increasingly believe that may happen when Iranians go to the polls, concluding a hotly contested campaign. But an Iranian proverb says when you throw an apple in the air it turns 100 times before it hits the ground. This year's election campaign has been full of surprises. On Monday, Mousavi campaigners themselves were surprised when at least 100,000 supporters filled both sides of the 18km-long Vali-Asr Avenue in Tehran in response to a call to form a human chain along the street. Traffic on the avenue and side streets was blocked by 5pm, and well past midnight there were still thousands of people chanting and honking their car horns. Some newspapers went so far as to call the massive turnout a "green Mousavi tsunami". Vali-Asr Avenue, a four-lane boulevard lined with plane trees, runs from Rah Ahan Square in the city's poor south to Tajrish Square in affluent northern Tehran, and has many main squares along it. North, south and all points in between were green. The call seemed to draw people from every walk of life and age. Ahmadinejad supporters could be seen in the streets on Monday too, though in smaller numbers, riding motorbikes and in cars decorated with the Iranian flag, which his campaign has appropriated as its symbol. Tens of thousands of them had gone to Tehran's prayer ground to listen to a speech by the president, who arrived too late and left without delivering a speech. He reportedly got caught in the traffic created by the green wave of Mousavi supporters. But it was not only on Monday that such a huge crowd poured into the streets. These days, many people, especially the young, wake up late with voices hoarse from shouting slogans the night before. Thousands of them stay on the streets until dawn, chanting, distributing posters and pamphlets and having a good time. The amount of energy is astonishing. Yesterday afternoon and through the evening, Mousavi supporters again flooded the streets from Enghelab (Revolution) square to Azadi (Freedom) square. This time their numbers were in the hundreds of thousands. I had never seen so many people marching in Tehran except on the anniversary of the revolution. The crowd was getting even bigger when I left. Some of the slogans that supporters of candidates shout at each other on the streets have a sarcastic edge to them and some are funny. Few involve the words "down with" or "death". But this all comes to an end today, as a legal ban prevents campaigning for 24 hours before the election. The spirit on the streets is reminiscent of the first two years after the Islamic Revolution of 1979, when people were seen everywhere in big numbers, marching, protesting and getting into heated discussions. There was a huge degree of tolerance then, and this year tolerance is also quite high. There have been some scuffles between Ahmadinejad supporters and the "greens", but people intervene and separate the angry parties and no one is seriously hurt. Police have intervened only rarely, when things threatened to get out of hand. This year, fewer people are grumbling about the futility of voting. Turnout is expected to be high tomorrow. If that happens, analysts expect reformists will have a much greater chance of winning. Aside from the street rallies there are other scenes reminiscent of the days of high revolutionary spirit. On Tuesday at 9pm, cries of Allahu Akbar (God is great) drew me to my balcony in western Tehran. I was taken back to the 1980s when people yelled the same phrase from rooftops and balconies to show their support for the revolution and the Iranian soldiers fighting against Iraq. It was Mousavi supporters who revived the call from rooftops to show support for a man in whom many have invested high hopes to bring change to their lives. Everyone seems to agree that this year's election is different from all the previous ones. It is the first time Iranians have become so actively involved in a political movement in many years, particularly by taking to the streets in support of their candidates. For all that, however, many say it is change they want - not a revolution. "This change in the society's attitude to the election campaign is a huge development in itself," said a friend who is a supporter of Mehdi Karrubi, a reformist candidate running behind Mr Mousavi. "It shows that our people are moving towards a better understanding of democracy and its ways. Ahmadinejad may stay in power, but nothing will be the same afterwards." <br/>msinaiee@thenational.ae