Mahmoud Ahmadinejad is the latest in a long line of American bogeymen: Libya's Colonel Gadafy, Panama's Manuel Noriega, Serbia's Slobodan Milosevic, Iraq's Saddam Hussein and al-Qaida's Osama bin Laden, to name a few.

But by casting Iran's president in the prime target role of maverick evildoer, the Bush administration ignores the complex forces that brought him to power last year and his previously unsuspected political skills, both supporters and critics say. As domestic opponents have already discovered, underestimating Mr Ahmadinejad is tempting - and foolish.

The president's rising popularity owes as much to his common touch as US enmity. Many ordinary Iranians, while complaining about wages, inflation and restricted personal freedoms, approve of the Blair-like "national conversation" that Mr Ahmadinejad has launched through fortnightly provincial tours and rallies.

"He is a good man. He tries to do his best," said Saeideh, a student in Shiraz. "My family supported [Mohammad] Khatami [the former reformist president]. But it is good the way Ahmadinejad stands up to the Americans."

Mohammad Atrianfar, founder of the main opposition newspaper, Shargh, admitted that Mr Ahmadinejad had succeeded in cultivating a popular image, but questioned his authority. "My impression is that he is just a mouthpiece, an amplifier for various interests elsewhere," Mr Atrianfar said.

Anti-government intellectuals and secularists also attribute Mr Ahmadinejad's ascendancy to the backing of clerical hardliners, as well as the Revolutionary Guards and basij militia. They said the president owed his job to the supreme leader, Ali Khamenei, who was primarily concerned with establishing Iran's leadership in the Muslim world over the rival claims of Arab states such as Egypt.

Mr Khamenei is said to be gratified by Mr Ahmadinejad's hero status in the Arab world as a scourge of the Bush administration and champion of Palestinian rights. At the same time, western diplomats said there was evidence the president was "learning on the job". He had toned down his rhetoric and qualified last autumn's inflammatory remarks on the Holocaust and Israel, they said. He now says Iran simply wants justice (a key Ahmadinejad theme) for Palestinians and does not see why Muslims should pay for past European persecution of Jews.

Yet Mr Ahmadinejad is far from being a puppet of Iran's mullahs or clerics. A strong current of anti-clericalism permeates the Islamic republic 27 years after the revolution, largely the product of perceived corruption and abuse of power. His advancement came in part because, ironically, he was able to assume Mr Khatami's mantle as the "anti-status quo candidate", a source said.

The secret of Mr Ahmadinejad's success was that he had distanced himself from both the Islamic establishment and the discredited, mostly middle-class reformers of the Khatami era, building a third constituency among the working classes, younger voters and the less well-off.

Siamak Namazi, an independent Tehran political analyst, said: "Ahmadinejad represents the second generation of revolutionaries, the foot soldiers of 1979. They are the ones who fought the war against Iraq, they are the ones who suffered when Saddam used chemical weapons (whose components were supplied by the west). They are the ones who now get lectured by the west about WMD. They feel very suspicious about the west. They also feel the older generation sold them out." Mr Ahmadinejad was "politically right but economically ultra-left", he added.

Some see Mr Ahmadinejad as a product of the pre-revolutionary period in which Marxist ideas mingled with Sufi mysticism and Islamic spiritual values. His support for a centrally directed economy, continued state subsidies and more equal rights for women can thus be reconciled with his opposition to reform of Iran's inherently conservative, Islamic-based power structure.

All the same, economic mismanagement and inefficiency may yet be his undoing. "This is a sick economy dependent on the price of oil," said Vahid Karimi of the Institute for Political and International Studies. Structural weaknesses including lack of investment, a tiny private sector, and capital flight were not being addressed, a report by 50 prominent economists concluded. A fast-growing population was increasingly demanding more than the government was delivering, a western diplomat said. "They are squandering the oil windfall."

Mr Ahmadinejad's fall, if and when it comes, is unlikely to be the result of political insurrection, outside intervention, or his demonisation as America's new bogeyman. Its likely cause will be more mundane. In Iran, as elsewhere, it's the economy, stupid.