Wikipedia article: http://archive.is/CStjp

Dennis Hastert and Nancy Pelosi tried to protect him from investigation by the FBI. The investigation apparently started after a company in Jefferson's spouse's name allegedly received $400,000 from a tech company, allegedly in return for political favors. He was finally sentenced to 13 years in prison for corruption.

It is an interesting story, with the controversy around the separation of powers, and what the FBI can/should investigate.

It begs the question, what kind of allege-ing is required for the FBI to begin to investigate someone? The FBI raided his house and his office and videotaped him, in order to convict.