State Sen. Rachel Ventura, D-Joliet, had 60% of the vote with most precincts counted in the 43rd District.
Ventura was seeking reelection to a second term in the district that includes much of Joliet as it runs from Bolingbrook to the Wilmington area.
She was opposed by Jennifer Monson, an elected school board member at Minooka Community Consolidated School District 201.
With 96% of precincts counted, Ventura had 39,839 votes to 26,682 for Monson.