President Obama's controversial relationships with radical figures like Columbia University professor Rashid Khalidi have been well-publicized in recent years.
Prior to his academic career in the United States, Khalidi worked for Yasser Arafat's Palestine Liberation Organization when it was classified by the State Department as a terrorist group.
Less well-known is a cluster of Chicago businessmen who formed an Arab-American network at the heart of Obama's political apparatus. Ray Hanania, a Chicago-based Arab-American journalist and activist, described the network in a 2007 interview with Chicago magazine as "a small cluster of activists" in the business community who were politically involved.
Chief among them was Obama mentor Tony Rezko. Born in Aleppo, Syria, home of strongman Bashar al-Assad, Rezko migrated to the U.S. in the late 1970s and built a political and financial empire in Chicago and Springfield, the Illinois capital.
Rezko is now serving a 10-year federal prison sentence following his convictions on federal fraud and bribery charges related to disgraced Gov. Rod Blagojevich and state contracting.
Rezko offered Obama a job at his Rezmar Corp. after he finished at Harvard Law School, but the new lawyer instead accepted a position at a Chicago firm with close personal and professional ties to Rezko. Their relationship steadily deepened in the years thereafter.
For example, Obama asked Rezko to assess the $1.6 million Hyde Park/Kenwood home that he and Michelle were considering buying in 2005, a controversial transaction that Rezko's wife assisted by purchasing an adjoining lot for $625,000. (The owner of the home and adjoining lot insisted that they be sold together.)
Rezko and his Arab-American business associates have contributed hundreds of thousands of dollars to Obama's political campaigns. Following Rezko's conviction, though, Obama donated to charity at least $85,000 in Rezko contributions to his 2008 presidential campaign.
The Chicago Sun-Times estimated Obama received at least "$168,308 from Rezko and his circle," while ABC News put the total to be as much as $100,000 higher than the amount claimed by Obama.
While he was in the Illinois Senate, Obama helped key Rezko associates gain appointments to the state board that controlled health facility contracting for building expansions.
Once his associates were appointed, Rezko sought kickbacks from contractors favored by his friends in a process that became the heart of the federal case against him.
When Obama became chairman of the state Senate health committee that oversaw appointments to the medical board, among his first acts was to gain fast-track passage of a bill to reduce the board from 15 to nine members, thus making it somewhat easier to gain the panel's approval for contracts.
Rezko then used his connections with Blagojevich to stack the restructured board with his political cronies. Their appointments were confirmed by Obama's committee, then sent to the Senate floor.
Soon thereafter, contributions from Rezko and his health board allies began pouring into Obama's campaign coffers, according to federal and state campaign finance data.
Rezko associate Dr. Michel Malek, for example, donated $15,000 to Obama after gaining appointment to the health board.
Dr. Imad Almanaseer, another Rezko ally appointed to the health board, initially gave Obama $3,000. Over the next three years, he and members of his family donated nearly $10,000 more to Obama.
Fortunee Massuda, another Rezko associate, donated $2,000 in January 2004 shortly after winning her assignment to the key panel.
Other Rezko allies who were not on the health board also contributed to Obama. Elie Maloof was granted immunity by federal prosecutors after he told U.S. attorneys he funneled two $10,000 contributions to Obama through Rezko. Prosecutors noted Maloof's assertion in their opening arguments at Rezko's trial, but no additional charges were filed.
Rezko business partner Abdelhamid Chaib donated $10,000 to Obama, then was convicted on federal corruption charges in 2010 after trying to pressure a Chicago hospital executive to steer contracts to Rezko companies.
Another Rezko partner, Ali Ata, was a key witness during Rezko's 2008 federal corruption trial. He donated $5,000 to Obama's campaign and claimed to have given an additional $10,000 in "straw donations."
Ata was a former president of the Chicago Chapter of the Arab-American Anti-Discrimination Committee.
Ata also was an investor with Rezko and Nadhmi Auchi, an Iraqi-British businessman and former Iraqi Baathist who was on a terror watch list and thus barred from entering the United States.
Rezko asked federal authorities in 2004 to permit Auchi to join him in Chicago for a business deal, according to the New York Times.
Stuart Levine, Rezko's former partner and the government's star witness in the Rezko trial, testified that Obama met Auchi at a private Rezko reception held at Chicago's Four Seasons hotel.
Auchi wired $3.5 million to Rezko during the 2008 trial. Federal prosecutors asked for Rezko's bail to be revoked when they discovered the Auchi wire transfer.
Another Rezko supporter was Mustafa Abdalla, who donated $1,000 to Obama. Abdalla put up property as collateral for Rezko's bail.
Rezko was a generous financial supporter of Chicago-based Arab-American activist groups, including the Arab American Democratic Club, or AADC, and the Arab American Action Network, or AAAN.
Rezko was involved in the AADC with Khalil Shalabi. Shalabi was fired from a state government job in 2007 after the Illinois inspector general reported he had been fundraising at work for Rezko and Blagojevich.
The Obamas attended several AAAN dinners, including one honoring Khalidi. More recently, Hatem Abudayyeh, AAAN's executive director, attended an April 22, 2010, Obama policy briefing, according to White House visitor logs.
In September 2010, FBI investigators raided Abudayyeh's Chicago home reportedly seeking evidence of AAAN being used as a conduit for funding to the Popular Front for the Liberation of Palestine and other Middle Eastern terrorist groups.