At the mosque of Jamkaran, 110km south of Tehran and just east of the holy city of Qom, tens of thousands gather on Tuesdays to pray and drop messages for the "missing" imam into a well.
Abul-Qassem Mohammed, the 12th leader whom Shia Muslims regard as a successor to the prophet Mohammed, entered "occultation" in 941 and will one day return to rule justly before Judgment Day.
In the women's section by Jamkaran's well, Mina, 18, faints, only slowly regaining consciousness and whispering. "Last night she dreamed the 12th Imam asked her to come," says an older female relative. "Don't interrupt, she is talking to the Imam."
Pilgrims then take small pieces of Mina's green scarf torn up by her relatives.
Veneration of the 12th Imam is common among Iran's 68m population, whose religious practices mix piety, respect for learned clerics and age-old mysticism. But the new president, Mahmoud Ahmadi-Nejad, has placed a special emphasis on the 12th Imam, even referring to him in his October United Nations speech.
While many analysts highlight Mr Ahmadi-Nejad's background in the Basij Islamic militia or his promotion of former Revolutionary Guards to key positions, the discreet talk among those close to the regime is more about his religious beliefs.
Mr Ahmadi-Nejad has not only reached out to millions of pious Iranians through venerating the 12th Imam, but has engaged with deeply conservative religious groups that shunned politics for much of the 26 years of the Islamic Republic.
The 1979 political revolution led by Ayatollah Ruhollah Khomeini broke with such conservatism, says Mohammad-Ali Abtahi, cleric and former reformist vice-president. "Unlike Ayatollah Khomeini, most clerics resisted change, distrusted politics and emphasised the 12th Imam's return as the only way to attain justice," he says. "After the revolution, they came to accept the Islamic Republic but not its progressive aspects."
Hojjatiyeh, a group laying special stress on the Imam's return, was banned by Ayatollah Khomeini in the revolution's early years. But a crucial development came in 1989 when, after Ayatollah Khomeini died, Ayatollah Ali Khamenei replaced him as Iran's supreme leader.
Lacking his predecessor's political and religious credentials, Ayatollah Khamenei turned to religious conservatives for support. "Ayatollah Khamenei spoke of Mohammad Taqi Mesbah-Yazdi [seen by many intellectuals as Iran's most uncompromising cleric] as a great teacher," remembers Mohsen Kadivar, a reformist cleric and philosophy professor. "Later Mr Ahmadi-Nejad also looked to such conservatives for legitimacy."
Few doubt that previously unorganised, grassroots religious groups played a key role in Mr Ahmadi-Nejad's election campaign. "He rode a wave using mosque-based organisations and even maddahs [religious singers] to gain support," says Mr Abtahi. "But these songs aren't political, they're not praising the Islamic Republic, only the 12th Imam."
For political leaders to seek backing from popular religion, mystics or even millennialists is hardly new in Iran. The Safavid dynasty (1501-1722), which converted the country to Shi'ism, sprung from a small Sunni sect whose followers believed its leader was divine. The Shah of Iran, often seen as a secular moderniser, allowed mobs to attack Bahais, a sect seen as heretics by conservative Shia.
Three months after Mr Ahmadi-Nejad became president, whispers about his view of the 12th Imam are growing. According to one rumour, as mayor of Tehran he drew up a new city plan for the imam's return.
The culture ministry last month denied the government had dropped a letter pledging loyalty into Jamkaran well. But an early cabinet decision allocated the equivalent of $17m for Jamkaran. And Mr Ahmadi-Nejad's promises to eliminate injustice, corruption and unemployment have more sense of "heaven on earth" than mundane government targets.
"His behaviour shows he has more important goals than politics," says Mr Abtahi. "He speaks with the confidence of someone who has received God's word. Whether genuine or a means to power, this is a new discourse for the Iranian revolution." READ MORE
Some senior clergy are alarmed. Ayatollah Ahmad Khatami, a conservative, has attacked maddahs for singing about dreams and "fake meetings" with the imam.
In foreign policy, officials worry an emphasis on the 12th Imam not only puzzles Europe and Russia while Iran tries to revive talks over its nuclear programme but alienates Sunni, a majority in the Muslim world, who do not share the Shia view of the Imam's return.
The consequences of Mr Ahmadi-Nejad's religiosity are also uncertain for Ayatollah Khamenei, to whom many look to rein in the president. "So far, the leader has seen Mr Ahmadi-Nejad as loyal, someone who should reach the 12th Imam through him," says a senior reformist. "But this is an unstable situation."
"Mr Ahmadi-Nejad's project must fail," says Mr Abtahi. "He is caught in the paradox of those who understand religious mystery in a physical [literal] way. Of course, we must pray for the return of the imam, but [in government] we must also tackle inflation and unemployment."
