Illinois lawmakers are scheduled to be in Chicago Monday to hear hours of public testimony about one of this year’s most pivotal topics: legislative redistricting.

The contentious process sets boundaries for lawmaker districts using U.S. Census data. Legislative maps get redrawn every ten years, and it’s never pretty. There are winners and losers. Some communities gain influence, others lose it; some lawmakers get their dream constituency, others get boxed out.

Illinois Democrats hold the map-making pen this year, as they control both chambers of the legislature and the governor’s office. State Sen. Kwame Raoul heads the Senate redistricting committee, which is holding the first of at least five public hearings Monday afternoon.

On Monday the committee will hear from, among others, the Asian American Institute, Mexican American Legal Defense Fund and West Side branch of the NAACP.

A recently passed law requires an Illinois House committee to hold similar meetings, but that panel has not yet been formed.