CHICAGO (AP) — Once lauded as the longest-serving legislative leader in American history, Michael Madigan will enter a federal courtroom this week on charges he used his vast influence to run a “criminal enterprise” to amass even more wealth and power. The former Illinois House speaker is charged in a multimillion-dollar racketeering and bribery scheme that included the state's largest utility, ComEd. From wiretapped calls to video-recorded meetings, much of the evidence has been previewed in open court.

A sweeping investigation of public corruption has already produced convictions of legislators and Madigan’s former chief of staff . But starting Tuesday, as potential jurors first report to court, the spotlight turns to the Chicago Democrat who was once considered the most powerful force in Illinois politics. “This is the top of the mountain here, the very very top,” former federal prosecutor Phil Turner said.

Here is a closer look at the case: Madigan, speaker for more than three decades, is charged in a 23-count indictment with racketeering conspiracy, using interstate facilities in aid of bribery, wire fraud and attempted extortion. Federal prosecutors allege he exploited not only his role as speaker, but other positions of power, including Democratic Party of Illinois chair. He also is accused of benefiting from private legal work illegally steered to his law firm.

Madigan’s mission was to enhance “his political power and financial well-being while also ge.