In Ads, GOP Stresses Obama's Ties to Chicago Developer

"At that stage in his life, Barack was looking for people who were willing to help him. And Tony was willing to help him." said Anthony Licata, a Chicago lawyer and longtime Rezko acquaintance.

Over the next decade, Rezko contributed or helped raise as much as $250,000 for Obama. (Obama's campaigns now have donated to charity $159,000 in contributions linked to Rezko. Rezko has not donated to, or raised money for, Obama's presidential campaign, officials said.)

Obama said he had performed no favors for Rezko. Last year, the Chicago Sun-Times discovered a 1998 letter from Obama urging local officials to fund a senior living project proposed by a firm controlled by Rezko and a partner. The campaign and Rezko's attorney later said that Rezko did not request the letter.

Over time, Rezko and Obama met socially. Obama told reporters that he and his wife, Michelle, once visited the Rezko home on Lake Geneva in Wisconsin and that the two couples dined together at a Chicago restaurant.

Rezko, a native of Syria, has an impressive life story, Brint said.

"He came over here, he didn't speak any English," he said. "He built strong relationships, people trusted him."

Rezko also raised money for Illinois Gov. Rod Blagojevich (D) and screened candidates for posts in his administration. Obama said he had "formal discussions" with Rezko about a job for Eric Whitaker, a physician and friend. In 2003, Blagojevich named Whitaker director of the Illinois Department of Public Health.

Obama was elected to the U.S. Senate in 2004 and the next year decided to buy a house in Chicago priced at $1.95 million. He later said that Rezko toured the home and advised him to buy it. Around the same time, Rezko's name was surfacing in connection with reports about questionable dealings in local government.

In June 2005, Obama and his wife closed on the house for $300,000 less than the asking price. That same day, in what Obama has said was an independent transaction, Rezko's wife, Rita, bought a lot that served as the house's side yard for the full asking price of $625,000.

In January 2006, Rita Rezko sold the Obamas one-sixth of the lot for $104,000, one-sixth of the original purchase price. Obama acknowledged later that he "should have seen some red flags" in making the purchase.

In October 2006, federal authorities culminated their three-year investigation of the Illinois government. Rezko's trial, which began in March, detailed how he used political influence to collect kickbacks from companies seeking state business.

In a statement, Obama said: "This isn't the Tony Rezko I knew." Rezko's next hearing is set for Dec. 16.

Polling editor Jon Cohen and research editor Alice Crites contributed to this report.