Flowering rebellion could fade away as fast as it blossomed

Instead of choosing a leader who will coax it back to engagement with the world, the government in Tehran will be led for another four years by the small-minded Mahmoud Ahmedinejad.

The brave protests by supporters of defeated electoral rival Mirhossein Mousavi could peter out soon.

Ahmedinejad's thugs have few scruples. The world is watching, horrified at the brutality, but seems unwilling as well as powerless to intervene.

The most powerful domestic challenge to the Islamic republic since the revolution that overthrew the Shah 30 years ago will likely fade as fast as it blossomed.

President Ahmedinejad and his political master, Supreme Leader Ayatollah Ali Khamenei, will be free to consolidate their rule at home and possibly boost Iran's influence across the Middle East.

Iranian elections usually have two rounds. No one wins the first round with the required 50 per cent so the two strongest candidates are pitted against each other a week later.

In the past it has been a controlled choice rather than a directly rigged one but this time Khamenei clearly decided Ahmedinejad had to win straight off.

Khamenei, the real power in Iran, has a morbid fear that his regime can be overthrown in a "velvet revolution", of the type that overthrew Czechoslovakia's communist government in 1989.

Mousavi seemed to have been gaining popular momentum, pulling in the votes of those embarrassed by Ahmedinejad's rantings against the United States and Israel and those who realised that his economic promises were too often just hot air.

It is likely that Khamenei - who, 20 years ago this month, became leader on the death of Ayatollah Khomeini - decided the manipulation necessary to ensure Ahmedinejad's victory in a second round of balloting might have been too controversial.

Best to move fast. Perhaps Khamenei misjudged the strength of support for Mousavi but now the minor concession of asking the Council of Guardians to review allegations of rigging is unlikely to change the outcome.

Most Iranians will probably accept the result or judge protests to be futile. Khamenei, who controls the military, the security services and the media, will be free to consolidate at home and continue Iran's ideological expansionism abroad.

Co-religionist Shia Muslims in Lebanon, whose Hezbollah party was defeated in elections last week, will be able to mount a comeback.

Shia communities in Sunni Arab states like Saudi Arabia and Bahrain will be reminded that they have powerful support from Tehran.

Ironically, Mousavi is as much a child of the Iranian revolution as Ahmadinejad or Khamenei. He was prime minister in the Eighties (a role that no longer exists) when Khameni was president and Khomeini was supreme leader.

Indeed, Iran's nuclear weapons programme - little more than a dream in the Shah's time - was revived in 1987 under Mousavi.

The programme, almost undeniable but still denied, could be accelerated.

In Khamenei's eyes, a nuclear bomb is the ultimate guarantor of the Islamic revolution.

But Mousavi represented a rejection of Iran's current abrasive style and for many symbolised a hope that Tehran could change.

The election outcome is a major challenge for the US, where yesterday President Obama said he is "deeply troubled" by the violence.

But he did stop short of alleging fraud, instead giving "respect to Iran's sovereignty".

History will judge whether those words will keep open the diplomatic door or be seen as ignoring the tears of those who cried "foul".

Simon Henderson, who was a Financial Times correspondent in Tehran during the 1979 revolution, is a senior fellow at the Washington Institute for Near East Policy.