WASHINGTON — Something remarkable happened last week at the gold-domed shrine to Ayatollah Ruhollah Khomeini, the founder of Iran's Islamic Republic and its most revered figure, in Tehran.

At ceremonies marking the 21st anniversary of Khomeini's death, religious hard-liners and members of the Basiji militia heckled Khomeini's grandson, Hassan, for sympathizing with the opposition Green Movement and forced him off the stage.

The unprecedented disruption provided revealing insight into the state of Iranian politics a year after the biggest upheaval since the country's 1979 Islamic revolution, according to U.S. officials, foreign diplomats and private analysts.

Dissent isn't tolerated, fissures are widening among the ruling conservatives who claim to be Khomeini's heirs and Iranians' deep dissatisfaction with their government hasn't gone away.

Iran is in "political purgatory," said Abbas Milani, the director of Iranian studies at Stanford University.

What ignited the protests last year was the fraud-stained re-election of President Mahmoud Ahmadinejad on June 12. Ahmadinejad remains in power, however, dashing the hopes of anyone who thought the unrest might lead to the reform — or even the overthrow — of Iran's theocracy.

After weeks of street demonstrations, regime security forces cracked down ferociously, killing dozens of civilians and arresting thousands more.

In the months that followed, academics, journalists, labor leaders and others were subjected to arrest, intimidation and abuses in prison, according to Amnesty International and other human rights groups.

In a sign of the Green Movement's weakness, former presidential candidates Mir Hossein Mousavi and Mehdi Karroubi on Thursday canceled protests that had been called to mark the anniversary. Mousavi and Karroubi, who haven't led the opposition so much as been led by it, expressed fears that security forces would harm their supporters.

"The opposition has pulled away from a strategy focused on large-scale street demonstrations and is opting for a more long-term civil rights-style movement," Persia House, an analytical unit of the consulting firm Booz Allen Hamilton, wrote in an assessment this week. "As was the case in the long run-up to the '79 Iranian revolution, this movement's success in changing the country's political landscape cannot be measured in months but rather in years."

The grim standoff in Tehran has left U.S. policy on Iran in purgatory, too.

On Wednesday, the U.N. Security Council imposed a fourth round of economic sanctions on Iran over its suspected nuclear-weapons program. It's that issue, and Iran's backing for militants throughout the Middle East — not Iran's domestic political scene — that's dominated President Barack Obama's attention.

The latest sanctions, which expand financial restrictions, an arms embargo and measures aimed at the powerful Islamic Revolutionary Guard Corps, are likely to pinch Iran's economy further, Western diplomats say. Iran's leaders maneuvered to avoid them. However, it's unlikely that they'll prompt Iran to stop enriching uranium, which could be used for nuclear weapons.

A British diplomat argued that the sanctions also could affect Iran's increasingly tense politics, affecting the merchant class known as bazaaris and middle-class technocrats.

"We're trying to influence the politics inside Iran to alter the cost-benefit analysis for the regime," said the diplomat, who requested anonymity to speak more frankly.

Accurate information on Iran's opaque, overlapping leadership structure is hard to come by in the best of times, and in the last year it's become harder. The regime has cracked down on Iranians' use of the Internet to send unofficial news abroad. Further, while many U.S. news outlets, including McClatchy, were allowed in to cover last year's elections, most are excluded now.

So the country's outward calm may be misleading, according to U.S. officials, diplomats and analysts who follow Iran closely.

The treatment of Khomeini's grandson is part of what appears to be a risky strategy for Iran's leaders, one that could even estrange large portions of Iranian society.

The supreme leader, Ayatollah Ali Khamenei, came out of the crisis stronger, but he rules from a shrunken base, dependent on the increasingly powerful Islamic Revolutionary Guard Corps. Other conservatives, and even much of Iran's once-powerful Shiite Muslim clergy, have been pushed to the sidelines.

"The color spectrum of this regime now ranges from pitch black to dark gray," said Karim Sadjadpour of the Carnegie Endowment for International Peace.

Ahmadinejad, the public face of Iran's government, owes his position to Khamenei, but there are reports of growing tensions between them. The uncompromising Ahmadinejad also has alienated many erstwhile allies, officials say.

"He thinks he's the quarterback for the regime, but doesn't have a whole lot of willing blockers. This isn't Joe Theismann and the Redskins Hogs," said one U.S. official, making a comparison to an old Washington Redskins football lineup. He asked not to be identified because he wasn't authorized to speak for the record. "He's alienated a hell of a lot of linemen."

Few in the West predicted the historic post-election tumult, and U.S. officials concede they have little clue what might spark Iran's opposition back into the streets.

The regime — whose leaders came to power from the street 30 years ago — has proved deft in recent months at repressing dissent without creating martyrs.

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