Tim Whelan of Wheaton has unseated longtime DuPage County Forest Preserve Commissioner Mike Formento of Glen Ellyn in their race for the Republican nomination in District 4.
With all 134 precincts reporting, Whelan received roughly 54 percent of the vote, while Formento garnered about 46 percent.
Whelan will advance to the November general election where he will face Democrat Robert "Bob" Flesvig of Wheaton, who ran unopposed Tuesday in his party's primary. The winner's term will either be 2 or 4 years. The length will be determined by lottery after the November election, in which all seats are open.
District 4 includes all or parts of Addison, Carol Stream, Downers Grove, Glen Ellyn, Glendale Heights, Lombard, Winfield and Wheaton.