The Baath Party ruled Iraq well before Iraqi President Saddam Hussein seized full control -- and it is likely to haunt Iraqi politics long after he disappears.
Most experts think that a new regime will depend heavily -- at lower levels -- on former Baathists.
The Arab Baath Socialist Party gained a totalitarian grip over nearly all aspects of Iraqi society since its first brief lurch to power in 1963 and its final takeover in 1968.
Saddam -- who reportedly got his start in the party as a clandestine killer -- was a force behind the scenes starting in the late 1960s but did not formally grab control until 1979.
American officials say uprooting the Baath is a major goal of their war against Saddam's regime.
But that may not be easy. The top ranks of the bureaucracy, the military and schools are dominated by Baath loyalists and generations have been indoctrinated with the party's theory of Arab supremacy. Lower-level members have managed the institutions of government on a day-to-day basis.
"This is a technocratic society. ... We are going to have to rely on these technocrats to run the country," said historian Phebe Marr, a specialist on Iraq.
"A lot of people in the Baath could emerge in one way or another as political players in the country," said David Mack, vice president of the Washington-based Middle East Institute, a think tank that includes many former U.S. diplomats.
He noted some Baath members have split from Saddam and fled the country. Others joined the party as a convenience, he said, explaining "a huge number of Baathis ... are card-carrying members of the party because it is about the only way you could get a government job."
As many as 1.5 million of Iraq's 24 million people once belonged to the party in some way. But only about 25,000 to 50,000 were full-fledged members -- the sort of elite targeted by those who want to end the party's influence.
In post-Saddam Iraq, top Baath members "should never even be allowed ... to even approach an educational institution, or a media institution, or a military institution," said Iraq specialist Amatzia Baram of the University of Haifa, speaking at a seminar on Iraq's future.
The party was founded in Syria in 1943 and spread around the Arab world, promoting Arab superiority and Arab unity with a violent, Soviet-style party structure.
It took power in Syria in 1963 and created branches in many Arab countries, bitterly squabbling both with established governments and rival, communist revolutionaries.
"In the 1970s when they had a lot of money, it was fairly attractive," said Marr. "It attracted a lot of people ... who overlooked the repressive factor. It was a modernizing party, secular."
After 34 years of brutality, the attraction long ago faded for many Arabs.
"I have no doubt in my mind that almost all people in Iraq really want to be rid of this regime and Saddam ... because they think he's a disaster," Marr said. "We are welcome to throw him out, but that does not mean Iraqis will welcome foreign occupation."
Many experts say a lengthy or heavy-handed U.S. rule over Iraq will inflame the sort of nationalist passions that helped the Baath come to power.
If the United States "stays in Iraq, which will make it unpopular, the Baath may have a future," said historian Rashid Khalidi of the University of Chicago.
He compared it to the Communist Party in the Soviet Union, which was once an object of hatred, but re-emerged under various names in several post-Soviet bloc states.
"Over time these parties reinvigorate themselves, shed their old image and come to represent something else," Khalidi said.