According to a story in The New Yorker, an investigation into real estate corruption ultimately caught the governor of Illinois trying to sell Barack Obama’s Senate seat: Whistle-blower by Nina Burleigh.
According to the story, an Illinois hospital was having trouble getting permits from the planning board. That is until they agreed to hire a certain contractor. That incident started U.S. Attorney Patrick Fitzgerald’s Operation Board Games. As the probe widened, more wiretaps were put in place, and more corruption was exposed. Eventually, recording Blagojevich discussing the sale of Obama’s Senate seat.