The stakes could scarcely be higher, but it is the lowly potato that has been grabbing attention.
The Government is handing out 400,000 tonnes of free spuds in rural towns. It says that it is merely distributing the surplus from a bumper crop, but Mr Ahmadinejad’s opponents accuse it of bribing the poor. “Death to potatoes,” they chant at rallies.
The spat is instructive. To much of the world, the election is about the nuclear ambitions of a pariah state. To most Iranians, the economy is the main issue. Mr Ahmadinejad’s rivals are savaging the record of a President who took office promising to give all Iranians a share of the oil wealth.
Iran has enjoyed revenues in excess of $300 billion, but the poor are worse off than before. By spending those revenues as if there were no tomorrow he has sent inflation, rents and property prices spiralling upwards while failing to tackle rampant unemployment.
He is seeking to divert attention from the economy by focusing on Iran’s nuclear programme, a source of pride to most Iranians, and his refusal to bow to Western demands that he should suspend it. He has compared Iran’s critics to dogs, declaring: “If you retreat, they attack. If you attack, they retreat.”
Last week Iran test-fired a missile capable of hitting Israel and Western Europe, in what appeared to be a staged show of power before the election. “Now we have more than 7,000 centrifuges [to enrich uranium] and the West dare not threaten us,” Mr Ahmadinejad boasted this week.
His opponents all say that they will continue the nuclear programme, which they claim is for civilian use only. In an unusually outspoken campaign, however, Mir Hossein Mousavi, Mr Ahmadinejad’s most prominent rival, and the other reformist candidate, Mehdi Karoubi, are accusing Mr Ahmadinejad of isolating Iran with his fiery rhetoric, and promise to pursue a less abrasive foreign policy.
Mr Ahmadinejad, 53, is expected to win. He appears to have the backing of Ayatollah Ali Khamenei, the Supreme Leader, and the Government’s considerable resources. He can count on millions of votes from the security forces and the Basij — the morality police. The populist President, who has pointedly visited and distributed largesse in every one of Iran’s 28 provinces, is still the darling of the devout and rural poor.
An upset is not impossible, however. Mr Mousavi, 67, is a popular former Prime Minister remembered for steering Iran through the turmoil of its war with Iraq. He advocates economic liberalisation and greater social freedoms, and his wife, Zahra Rahnavard, is breaking with tradition by publicly campaigning with him. He is chasing the urban and youth vote in a country where three quarters of the 70 million people are under 30.
About 475 people, including 42 women, applied to run for president, but the senior clerics of the Guardian Council only permitted four men to run in this curious hybrid state; part theocracy and part democracy. The other two candidates are Mr Karoubi, 72, a cleric and former parliamentary Speaker, and a hardliner named Mohsen Rezaei, 54, a former commander of the Revolutionary Guard.
They stand little chance of winning but could split the reformist and conservative votes respectively. Mr Ahmadinejad hopes that potatoes have electoral potency. He needs 50 per cent of the vote, or he will face a much more perilous second round against his strongest opponent.
• A suicide bomb detonated outside a mosque in the Iranian city of Zahedan yesterday killed 15 people and injured 50. Zahedan, near the Pakistani border, has witnessed clashes between police and drug dealers in the past.