ABC7 has learned that since late last summer, the congressman has worked with federal prosecutors, informing on an alleged Blagojevich administration scheme two and half years earlier.
The meeting in June of 2006 at a Gold Coast hotel included Congressman Jesse Jackson, Jr. and Blagojevich fundraiser Antoin "Tony" Rezko.
The topic was a proposed third airport at Peotone, Jackson's pet project which needed more state money. Rezko allegedly demanded that the governor be given control of the airport's board. Jackson refused and state support for the project stopped.
Then last summer, weeks after Rezko was found guilty of un-related corruption, the U.S. Attorney's Office interviewed the congressman as a possible witness against the governor in the Peotone matter.
And sources tell ABC7 that Jackson has been in regular contact with the feds and has told the government that in 2003 Blagojevich denied the congressman's wife Sandi an appointment as Illinois lottery director because Jackson would not donate $25,000 to the governor's campaign fund.
Hours before Blagojevich and his chief of staff John Harris were arrested, Jackson says prosecutors gave him a 'courtesy call' to let him know he was mentioned in the criminal complaint.
The U.S. attorney may have been referring to Jackson when he issued a warning to reporters last week.
"There may be people who had no idea what was going on...who had no idea they were being discussed," said Patrick Fitzgerald, U.S. attorney. "We ask that the press in particular not cast aspersions. This complaint is only about the two people who were charged."
A U.S. attorney's spokesman said of Jackson's role months ago in the Blagojevich case: "We don't confirm or deny the contacts. We have consistently refused to comment on the status of any individual not charged in this investigation."
Jackson supporters ABC7 talked to on Monday want the U.S. attorney to give the congressman a clean bill of health so to speak.
In1998, then U.S. Attorney Scott Lassar did that for Republican gubernatorial candidate George Ryan. Ryan was eventually convicted of corruption and now sits in a federal prison.