I have been following the Rezko case and I don't really see the risk to Obama. I have not seen any indications that Obama directed any of Rezko's illegal activities nor that he may have even been aware of his illegal activities (It is also evident that Obama did not spend a lot of time checking up on Rezko but that is hardly illegal).
I see no way Obama can be charged with a crime and impeached from office because of Rezko's activities.
If we were to impeach all the members of congress who accepted money from criminals it would be a pretty empty place.
However in this election where a candidate not wearing a "made in China" flag pin is a "big issue", this will probably be blown out of proportion.
A criminal giving money to a politician in Chicago. This is not exactly news folks
It will, however, give the political hyenas something to yap about instead of any real issue.