An investigation by Britain’s Guardian newspaper found that Rohrabacher had received thousands of dollars in donations from MEK supporters this year alone. The paper’s report adds that Florida Republican Rep. Ileana Ros-Lehtinen, the chair of the House of Representatives Foreign Affairs Committee, has accepted at least $20,000 in campaign donations from Iranian-American groups, or their leaders, that support the MEK. Other members of Congress were flown to France to address pro-MEK events, and a Washington lobbying firm received nearly $1 million to work on getting the MEK off the terrorist list, according to The Guardian.

“The multi-million-dollar lobbying campaign undertaken by the MEK and its supporters seems to have paid off,” said Jamal Abdi, the policy director of the National Iranian American Council.

The MEK took part in the Shiite Islamist overthrow of the U.S.-backed shah during the Islamic revolution of 1979. But the group quickly fell out with the ayatollahs, according to news reports, and thousands of its followers were killed, imprisoned or exiled. The MEK carried out a string of bombings and assassinations targeting regime officials. In 1997, the United States declared it a terrorist organization.

Under former Iraqi strongman Saddam Hussein, the MEK was given land just outside Baghdad upon which it built a self-sufficient camp, Ashraf, where the group’s female commanders tooled around in tanks and residents produced their own cola and ice cream. Throughout the day and night, fax machines chirped as MEK informants in Iran sent dispatches to the camp in Iraq.

But the U.S.-led invasion of Iraq ushered in an Iranian-friendly, Shiite leadership that was extremely hostile to the MEK, in part because the group is said to have aided Saddam in crushing rebellions in the 1990s. U.S. forces disarmed the camp, guarded the group for years and quietly helped facilitate repatriation to Iran for MEK defectors who agreed to an amnesty program offered by Tehran.

The Iranians who stayed in Iraq turned into virtual prisoners, an enclave of dissidents within the notorious Sunni Triangle during the bloody sectarian war of the mid-2000s. Iraqi forces raided the camp last year, leaving 34 residents dead.

The group uses footage of the attack to urge resettlement for its remaining members in Iraq. Third-party nations resisted admitting MEK members in large part because of the terrorist designation, activists said.

Last week, the U.N. mission in Iraq oversaw the transfer of 680 Ashraf residents to Camp Hurriya, which is to serve as a holding facility in Baghdad until a resettlement plan is reached. Of the 3,280 residents originally in Ashraf, only a small group remains to handle the closing of the camp, according to a U.N. statement.

Jonathan S. Landay contributed to this article.