Beyond the lavish palaces of the last Shah in north Tehran, beyond sweeping Enqelab (Revolution) Street, which cuts through the city center, even beyond the southern outskirts of the city’s rambling tenements, looms the Islamic Republic’s most notable landmark: the $2-billion tomb of its founder, Ayatullah Ruhollah Khomeini.

Though situated on a desolate piece of desert convenient only if you’re headed to the international airport, the enormous scaffolding-enclosed shrine, still under construction 20 years after the supreme leader’s death, is an essential part of the pilgrimage for devout Iranian Shi’ites.

Especially after this summer’s post-election chaos, the mausoleum has become ground zero for hardline conservatives. Supporters of opposition leader Mir-Hossein Mousavi rarely come down here to pray or seek blessing from the Imam; but fans of President Mahmoud Ahmadinejad are more concentrated here than in most neighborhoods of Tehran. Indeed, on a recent visit, hundreds of men with unkempt beards, ill-fitting pants and un-tucked white shirts — the trademark garb of the basij paramilitary vigilantes — milled about in the sprawling parking lot, said to be able to fit 20,000 cars. Dozens of tour buses sat idle after trucking in crowds from nearby Shi’ite strongholds like Iraq, while the license plates of the mostly run-down domestic-made paykans in the lot indicated that many came from the far corners of this country: Kermanshah in the west, Shiraz in the south, Yazd in the southeast.

A flimsy but in-your-face blue sign near the entrance displayed one of Khomeini’s best-known declarations: "We will stand until our last breath, last house, last drop of our blood to elevate the word of God.”

The shrine’s interior, reminiscent of an airport hanger, reflects Khomeini’s austere outlook.

During his rule, the Imam received all manners of dignitaries in a bare room at his daughter’s modest residence in the theological center of Qom, and refused to eat anything more extravagant than fruits, yogurt and rice.

In contrast, his sarcophagus has now been enclosed within a gaudy green-and-white cage, with the floor inside filled knee-deep in cash, bills inserted as donations by the pious. Some visitors are so zealous they openly weep at the sight of the tomb, including a few of the grim-faced bearded men.

But despite the presence of a conservative crowd, the hardline regime cancelled a major speech here earlier this month during Ramadan by the most prominent of Khomeini’s 15 grandchildren, Hassan Khomeini, who also happens to be administrator of the shrine.

Hassan, like many of his relatives, including at least three other grandchildren and a daughter of the Imam, has come out in support of the opposition movement.

The move was just the latest in a string of developments the past few weeks that reveal the regime’s efforts to maintain control, even at the risk of further alienating the family of the founder of the Islamic Republic. (See pictures of the rise and fall of the Shah of Iran.)

Therein lies the predicament for the regime. It has cast the street demonstrations as a supposedly Western-led, secular velvet revolution. But Shi’ites, who are the overwhelming majority of Iranian Muslims, believe that only an imam’s surviving lineage can accurately interpret his ideology. So to have so many Khomeinis jump ship set off alarms for the ruling hardliners.

The back-and-forth with Hassan Khomeini has become especially public. It began last February, when Hassan criticized the country’s military for encroaching into politics. In retribution, a newspaper connected to Ahmadinejad, a veteran of the elite Islamic Revolutionary Guards Corp (IRGC), accused Khomeini’s grandson of corruption and driving a BMW, marking the first time the regime insulted the Beit-e-Imam, the heirs of Khomeini.

Hassan then returned the favor in August when he left the country rather than attend Ahmadinejad’s second-term inauguration. Since then, state news agencies have launched an all-out media war against him, questioning his political credentials and suggesting he has been colluding with the "manipulators” — that is, opposition leaders like Mousavi and former president Mohammad Khatami. If history is any guide, the regime likely has the upper hand here.

Ayatullah Khomeini’s most promising son, Ahmad, died under suspicious circumstances at age 49. He had become critical of his father’s successor as Supreme Leader, Ayatullah Ali Khamenei, in the mid-1990s.

Indeed, there already seems to be an ideological purge in the works. In a recent interview, Khamenei’s representative to the IRGC declared that everyone "should obey the living Supreme Leader. Some people are sticking to Imam Khomeini’s ideas; they should know that [Khamenei] has run the country for the last 20 years.

The situation has changed.” Before the brutal post-election security crackdown, Khamenei at least tried to appear to be an impartial, albeit autocratic ruler, but that image was shattered by his June 19 speech bluntly threatening opposition protesters with violence.

If the Islamic Republic has substituted raw political calculation for the legacy of its founder, it has not yet trickled down to the pious Shi’ites from the provinces who gather at his tomb.

There, devotion and loyalty to the Imam still rings true. On a recent summer day, a group of women in head-to-toe chadors sat outside the main doors, chatting away, having a picnic. It was one of the few bright moments in a season of darkness.

TIME