Yet whatever the gripes of critics about the democratic value of the vote, by tomorrow the country will know which of two choices its electorate has made.

In one corner stands Akbar Hashemi Rafsanjani, 70, the former President, who espouses privatisation, cautious liberal reforms, negotiations over the nuclear programme and overtures to America.

In the other corner is Mahmoud Ahmadinejad, 49, the Mayor of Tehran and the soldier-son of a blacksmith, who advocates state-control of the economy with subsidies and handouts, a reverse of cultural reforms, the continuation of uranium enrichment and a stand-off with America.

It is the powerful showing of Mr Ahmadinejad in the first round last week that has dominated the run-up to today’s polls and sent shivers down the spine of his adversaries.

His campaign video is a masterful work of polemical imagery that has shot straight to the heart of the Mostazafan — the oppressed.

They are Iran’s workers, the poor and disaffected, those sick of corruption and the class divide, and he has captured their imaginations and votes.

The camera lingers on the residence of the previous Mayor of Tehran, a tenure taken by Mr Ahmadinejad in 2003.

Chandeliers drip from the high ceilings above marble floors, gilt bannisters lead the viewer through a spacious opulence of power never experienced by Iran’s shopkeepers and labourers, on toward the swimming pool, into the gymn, the sauna . . .

The timbre suddenly changes. A poignant violin is heard as we see the Ahmadinejad mayoral residence: a modest suburban-style home, sparse of furniture, his telephone lying on the carpet upon which he sits to do business. “Vote for me,” says the subtext. “I’ll not spend your money on trappings you will never enjoy. I’m just like you. Trust me.”

“Ahmadinejad has suffered in life,” said Orash Farahani, 29, who works in a Tehrani electrical store and will be giving the city’s mayor his vote today. “He has feeling for those who are hungry and poor. He’ll bring social justice to this country. The revolution was fought for the Mostazafan, but now we are forgotten again as the rich take over.”

Confidence in the predicted easy win for the favourite, Mr Rafsanjani, was shattered last week during the initial round of voting, when Mr Ahmadinejad, who is the bête noire of the international community, Iran’s liberals and its business sector, rose from nowhere to a robust second place, just 1.5 per cent behind his rival. His vote reflects not so much support for his religious conservatism or foreign policy, but for his social status and honesty.

Iran’s burgeoning working class sees little reward from Iran’s oil assets, which are currently selling at $59 (£32.50) a barrel.

The money disappears into a sump of corruption and mismanagement, opening a huge social schism between the small urban elite and the majority poor.

More than one third of the voters did not vote in the first round of the election and it is unclear whether they will be moved to back Mr Rafsanjani today. Most are believed to be reform-minded and disillusioned by the failure of outgoing President Khatami to bring them freedom.

Times Recommends

• Rio Tinto four held as China prepares case
• Diplomats must keep heads down and trousers up
• When in Rome should one make like Berlusconi?