At a time of partisan gridlock in the capital, one obscure cause has drawn a stellar list of supporters from both parties and the last two administrations, including a dozen former top national security officials.

That alone would be unusual. What makes it astonishing is the object of their attention: a fringe Iranian opposition group, long an ally of Saddam Hussein, that is designated as a terrorist organization under United States law and described by State Department officials as a repressive cult despised by most Iranians and Iraqis.

The extraordinary lobbying effort to reverse the terrorist designation of the group, the Mujahedeen Khalq, or People’s Mujahedeen, has won the support of two former C.I.A. directors, R. James Woolsey and Porter J. Goss; a former F.B.I. director, Louis J. Freeh; a former attorney general, Michael B. Mukasey; President George W. Bush’s first homeland security chief, Tom Ridge; President Obama’s first national security adviser, Gen. James L. Jones; big-name Republicans like the former New York mayor Rudolph W. Giuliani and Democrats like the former Vermont governor Howard Dean; and even the former top counterterrorism official of the State Department, Dell L. Dailey, who argued unsuccessfully for ending the terrorist label while in office.

The American advocates have been well paid, hired through their speaking agencies and collecting fees of $10,000 to $50,000 for speeches on behalf of the Iranian group. Some have been flown to Paris, Berlin and Brussels for appearances.

But they insist that their motive is humanitarian — to protect and resettle about 3,400 members of the group, known as the M.E.K., now confined in a camp in Iraq. They say the terrorist label, which dates to 1997 and then reflected decades of violence that included the killing of some Americans in the 1970s, is now outdated, unjustified and dangerous.

Emotions are running high as Secretary of State Hillary Rodham Clinton completes a review of the terrorist designation. The government of Prime Minister Nuri Kamal al-Maliki of Iraq has said it plans to close the camp, Camp Ashraf, by Dec. 31 and move the people elsewhere in Iraq in order to reassert Iraqi sovereignty over the land where it is located, 40 miles north of Baghdad.

Two earlier incursions by Iraqi troops into Camp Ashraf led to bloody confrontations, with 11 residents killed in July 2009 and at least 34 in April of this year. The M.E.K. and its American supporters say that they believe the Maliki government, with close ties to Iran, may soon carry out a mass slaughter on the pretext of regaining control of the camp.

If that happens, the supporters say, the United States — which disarmed the M.E.K. and guaranteed the security of the camp after the invasion of Iraq — will bear responsibility.

“We made a promise,” said Mr. Ridge, a former congressman and governor of Pennsylvania. “Our credibility is on the line. They’ve been attacked twice. How can we possibly accept assurances from the Maliki government?”

Mr. Ridge suggested that the M.E.K.’s implacable hostility to the rulers of Iran should be a point in their favor.

“In my view, if you’re a threat to Ahmadinejad,” — Mahmoud Ahmadinejad, Iran’s president — “well, the enemy of my enemy is my friend,” Mr. Ridge said. He noted that the M.E.K. had provided information on Iran’s nuclear program during the Bush administration.

The M.E.K. advocacy campaign has included full-page newspaper advertisements identifying the group as “Iran’s Main Opposition” — an absurd distortion in the view of most Iran specialists. The M.E.K. has hired high-priced lobbyists like the Washington firm Akin Gump Strauss Hauer & Feld. Its lawyers in Europe won a long fight to persuade the European Union to drop its own listing of the M.E.K. as a terrorist group in 2009.

The group’s spending, certainly in the millions of dollars, has inevitably raised questions about funding sources.

Ali Safavi, who runs a pro-M.E.K. group in Washington called Near East Policy Research, says the money comes from wealthy Iranian expatriates in the United States and Europe. Because “material support” to a designated terrorist group is a crime, advocates insist that the money goes only to sympathizers and not to the M.E.K. itself.

Congress has taken note of the campaign. A House resolution for dropping the terrorist listing has 97 co-sponsors, including the chairman of the House Intelligence Committee, Mike Rogers, Republican of Michigan. At a hearing this month, senators pressed the defense secretary, Leon E. Panetta, about the threat to Camp Ashraf.

A State Department spokesman, Mark Toner, said officials there were “working as quickly as possible” to complete a review of the M.E.K.’s terrorist designation. American officials are supporting an effort by the United Nations to resettle Camp Ashraf residents voluntarily to other countries, a process that is making slow progress.

Other State Department officials, addressing the issue on the condition of anonymity because it is still under deliberation, said that they did believe the 3,400 residents of Camp Ashraf were in danger as the Dec. 31 deadline approaches.

“We’re in constant talks with the Iraqis and the Ashraf leadership to show maximum flexibility on the closure of the camp,” one official said.

But the officials expressed frustration at what they described as the American supporters’ credulous acceptance of the M.E.K.’s claims of representing the Iranian opposition and of embracing democratic values.

In years of observation, the official said, Americans have seen that the camp’s leaders “exert total control over the lives of Ashraf’s residents, much like we would see in a totalitarian cult,” requiring fawning devotion to the M.E.K.’s leaders, Maryam Rajavi, who lives in France, and her husband, Massoud, whose whereabouts are unknown.

Moreover, the official said, the group is “hated almost universally by the Iranian population,” in part for siding with Mr. Hussein in the Iran-Iraq war in the 1980s. A State Department cable this year concluded that any indication of United States support for the M.E.K. “would fuel anti-American sentiment” in Iran and would “likely empower Iranian hardliners.”

In Iraq, the M.E.K. is also widely despised, especially by the country’s Shiite majority, because it is accused of helping the Iraqi dictator crush a Shiite revolt in 1991 — a charge the group denies. Because of deep Iraqi hostility, American officials argue that merely dropping the terrorist designation would not end the danger of attacks on the group.

While the M.E.K. carried out a campaign of attacks from the 1970s to the 1990s, mostly targeting Iranian officials, supporters say it has renounced violence and has not engaged in terrorist acts for a decade. The designation law, however, allows Mrs. Clinton to keep the label for a group that “retains the capability and intent to engage in terrorist activity or terrorism.”

Such a decision would outrage the American advocates of reversing the terrorist label.

Mr. Dean, chairman of the Democratic National Committee from 2005 to 2009, said the administration’s failure to act decisively threatened a “humanitarian catastrophe.” Mr. Mukasey said he did not believe the claim that the M.E.K. was a cult, but even if true, it was no reason to keep the terrorist listing. “These people are sitting in the camp, completely harmless,” he said.

Like other advocates, Mr. Mukasey said he had been paid his standard speaking fee — $15,000 to $20,000, according to the Web site of his speakers’ agency — to talk at M.E.K.-related events. But he insisted that the money was not a factor for him or other former officials who had taken up the cause. “There’s no way I would compromise my standing by expressing views I don’t believe in,” he said.

Artin Afkhami contributed reporting from Boston.

By SCOTT SHANE