The Iranian election controversy: what happens now?

What evidence is there of polling fraud?

The evidence so far is circumstantial but persuasive. The authorities behaved in an unusual way, shortcutting the normal three-day verification and declaration process, announcing an Ahmadinejad victory only two hours after polls closed. The Mousavi camp says the interior ministry told him earlier in the evening that he had won convincingly.

In the results published so far there are few of the geographical peaks and troughs that normally characterise fair elections. Ahmadinejad is even said to have won easily in his opponents' home towns. Tabriz, Mousavi's home base, normally has a strong bias for local ethnic Azeri candidates such as Mousavi, and he appeared to have particularly strong support there. Yet the official results gave 57% of the Tabriz vote to Ahmadinejad.

What can be done about it?

Not a lot, officially. Iran's supreme leader, Ali Khamenei, has issued a statement congratulating Ahmadinejad, apparently closing the door to an appeal or further official investigation. Other establishment figures, like Ali Larijani, the parliamentary speaker, have also closed ranks. However, Mousavi has so far shown no signs of publicly conceding and has called on the guardian council, the top legislative body in the Islamic republic, to annul the result.

Can Khamenei be challenged?

Under Iran's unique form of government, known as velayat-e-faqih – rule of the Islamic jurist – the supreme leader has far-reaching powers over the machinery of state. In theory, he can be dismissed by the assembly of experts, an elected body of Islamic scholars, currently chaired by Hashemi Rafsanjani, a former president, bitter enemy of Ahmadinejad, and a pivotal figure. However, the assembly has never before questioned the authority of the supreme leader, Ruhollah Khomeini, who created the system, or, since 1989, Ali Khamenei.

What are the authorities afraid of?

The election was initially seen as posing little threat to Khamenei and the top clerics. The guardian council, a conservative body of clerics, approved only four candidates out of more than 470 who registered. Mousavi had the reputation of an uncharismatic technocrat before the vote, but he became the focus of a pent-up desire for change. The raucousness of the Mousavi supporters and the profusion of green, his campaign colour, across the country, appears to have made the regime nervous about the possibility of an upheaval like the "colour revolutions" in eastern Europe. Hardliners saw the hand of Washington and the west behind such movements. They were unconvinced by the Obama administration's protestations that it was not continuing the Bush White House's strategy of regime change.

Is the idea of a reformist Iran just wishful thinking by the west?

The presidency of Mohammad Khatami, from 1997 to 2005 showed that it was possible for a reformist to be elected to high office, but it also showed that it was extremely hard – even for a president elected by a landslide – to bring about real change in the face of resistance from the supreme leader, the intelligence services and the revolutionary guard.

What happens next?

The next few days will reveal how far Mousavi supporters are willing to go to challenge the regime. They will also show how far the authorities are willing to go in suppressing dissent, whether they will clamp down on former safety valves for dissent like the internet. Either way, the events of the past few days have the makings of a turning point. It seems unlikely that Iran can carry on as before. It will be more repressive and quite possibly more turbulent.