The Los Angeles Times said that its examination of records found that Rezko, known as Tony, provided campaign donations at critical moments in Obama's rise from community activist and lawyer to state legislator, U.S. senator from Illinois and presidential candidate. Rezko is under a federal indictment on charges of extortion and conspiracy.
U.S. Sen. Hillary Clinton of New York brought up Rezko during a nasty exchange Monday night after Obama commented on her service on the board of Wal-Mart. Clinton referred to Rezko as a "slumlord."
Obama has returned $85,000 in contributions from Rezko. The Times says that over the years he received about $200,000 from the developer.
Rezko and his wife also helped Obama buy a historic $1.6 million Chicago house for $300,000 below the asking price.
One Chicago political activist says that Obama should have known better.
"Everybody in this town knew that Tony Rezko was headed for trouble," Jay Stewart of the Better Government Association, told the Times. "When he got indicted, there wasn't a single insider who was surprised."