CHICAGO — Ex-House speaker Michael Madigan, formerly the most powerful man in Illinois politics, “conspired to enhance and preserve (his) power and line his pockets” for years, prosecutors said at the outset of marathon closing arguments in Madigan’s corruption trial.

Madigan, 82, and his co-defendant, political ally and confidant Michael McClain, are accused of running a criminal enterprise designed to enrich the former speaker and his associates and increase his political power.