The Senate on Inauguration Day took action to limit the power of its legislative leaders. Meanwhile, House Democrats re-elected Mike Madigan as House speaker, ensuring he will become the longest-tenured legislative leader in modern American history.

At the end of his term in 2019, Madigan will be the longest-serving House speaker of any state in modern U.S. history.

The little-known legislative rules that govern the legislative process in the Illinois House of Representatives give the House speaker extraordinary power to orchestrate the legislative or political outcomes he or she wants. Those rules allow the speaker to influence the makeup of legislative committees; how lawmakers vote; and when, if ever, the bills get voted...