I Mahmoud Ahmadinejad of Iran has emerged as the global leader of the sartorially non-aligned – the club of bad-boy leaders who can call their looks their own. Ahmadinejad’s style is indeed distinctive, if only for its everyman anonymity: cheap loafers and white socks, open-necked shirts and polyester trousers, a five-day beard topped by a head of boyish hair, and all of it iced, most famously of all, with the beige Chinese windcheater.

Given Ahmadinejad’s millenarian spiritual vision and Holocaust denial sympathies, observers might expect something more dramatic from the Iranian president: more black, perhaps, or more leather. But that would be missing the point of the man – and of his look.

Ahmadinejad is an elected politician, and his look expresses the three things that won him office. First, his clothes send a signal to the biggest demographic in Iran. “I am like you,” they say to the country’s non-rural working and lower-middle classes. His jacket and slacks are the off-duty uniform of the small-town teacher, the house-proud bus-driver.

Secondly, there is the matter of what the president is not wearing: the neck tie, which the revolution has deemed the noose by which a free Muslim people hangs itself on the scaffold of western decadence. And the beard is the third element of Ahmadinejad’s style semiotics.

The Islamic face is a canvas of politico-spiritual symbolism, and Ahmadinejad works each variable in ways his constituents recognise. He does not shave (which Islam proscribes) but rather clips. Keeping the beard at a one-week length, he expresses solidarity with the Revolutionary Guards (he was once one himself) and neighbourhood militias that form the ground troops of the Islamic Revolution.

Any alternative in terms of facial hair would shock his supporters. In Iran today, a moustache refers back to the days of the Shah and is seen exclusively on secular men over 45. The full beard with shaved cheeks is popular among young Arabs – but it involves a razor, which the Prophet rejects, and has not taken root in Iran. And the last Islamic option, an untrimmed long or full beard, is for a lay Shi’ite the preserve of an enemy far more implacable than Jews or Christians: Sunni fundamentalists.

Educated Iranians, heirs to the oldest and most sophisticated uninterrupted culture on earth, find Ahmadinejad’s common aesthetic and rough features (sometimes mocked as simian) humiliating – as if these things were physical representations of their president’s equally embarrassing doctorate in Traffic Science. When Tehran’s drinking water became salty shortly after the presidential election of 2005, a joke went around by text – that a pair of Ahmadinejad’s socks had fallen into the reservoir. Last year Ahmadinejad himself received a joke about his personal hygiene on his phone, in one of Iran’s many random text-message blasts. (Strangely, his new party is called the Pleasant Scent of Service.)

But for all the noses that it turns up, Ahmadinejad’s physical presentation is undoubtedly intentional. When he surged from the back of the field to win the 2005 election, a large factor in his success was a widely distributed documentary about his modest lifestyle as mayor of Tehran. The film depicts Ahmadinejad driving to work in a 12-year-old Peugeot, living in his own small house, showing off the emptiness of his official residence.

Dress has defined Iranian politics for millennia. The matter of the woman’s hijab is the principal reduction of all domestic political questions in Iran for outsiders. The Revolution finds its iconography in the robes of the mullahs. The Shah’s splendid military uniforms emphasised his essential character as a Ruritanian petty despot. The last of the Iranian dynasties, the Qajars (1795-1925), are still loathed in Iran for blowing so much money in Parisian brothels that they had to pawn huge economic concessions to Europe. Their portraits in Tehran’s Golestan Palace show progression through the 19th century, from true Persian emperors to embarrassing Euro-wannabes. And the first great Persian kings, Cyrus, Darius and Xerxes, showed Iran’s power with huge stone inscriptions depicting subject nations defined by their clothes and hairstyles: Syrians in pleated robes, Babylonians in conical caps, Ethiopians with their tightly curled hair.

Ahmadinejad’s trademark jacket is made in China, according to his private office. It is available for between $8 (€6) and $20 (€15) in Tehran’s central bazaar, where he buys it himself, but the Ahmadinejacket is not selling well. Despite officially propagated reports that wearing one can get you better service in government offices, it is almost never seen on the streets of Iranian cities or towns.

This is no surprise. Ahmadinejad’s allies were trounced in the December elections – Iran’s first nationwide referendum on his popularity as president. His look worked well in 2005, on an outsider running against the establishment. But now the blacksmith’s son is president, and the look is selling a future of isolated fanaticism to which Iranians consider themselves ill-suited.