Downers Grove scientist Sean Casten narrowly edged Barrington Hills Plan Commissioner Kelly Mazeski to win the 6th Congressional District Democratic primary and will move on to face incumbent Republican Rep. Peter Roskam in what's expected to be a pivotal congressional race in November.
With 100 percent of 640 precincts reporting in five counties, Casten took in 19,082 votes, compared with Mazeski's 17,306 votes.
Final unofficial totals were not completed until early Wednesday because of a technical problem with closing hundreds of electronic voting machines in DuPage County.
Those ballots were key in the race, as Casten beat Mazeski by more than 4,000 votes in DuPage. Before DuPage results came in, Mazeski appeared to have a lead with roughly 29 percent of the vote compared to Casten's 27. When DuPage finished its count, Casten's votes amounted to 30 percent of the total, while Mazeski claimed 27 percent.
"We always expected it to be a close race," Mazeski said Tuesday night. "And I am proud of the grass-roots campaign that we have run."
Other candidates include Carole Cheney, a former congressional aide from Naperville, with 17 percent of the vote; Amanda Howland, a Lake Zurich attorney and College of Lake County trustee who lost a challenge to Roskam two years ago, with 13 percent; Becky Anderson Wilkins, a Naperville bookseller and city council member with 6 percent; and Ryan Huffman, a Palatine data analyst, and Jennifer Zordani, a Clarendon Hills attorney, with 4 percent of the vote each.
Anderson Wilkins also received a slight boost in vote totals when DuPage results came in, but the difference did not change the overall result.
The November general election is expected to be among the hottest and most expensive Congressional races in the state -- and one with national implications -- as Democrats target Roskam.
While Roskam, of Wheaton, has won the seat six times since 2006, Democrats believe he could be vulnerable because of the district's changing demographics and because of a groundswell of grass-roots organizations that have been energized in response to Donald Trump's victory in 2016.