Dold ran a strong race, but the district's heavy Democratic lean was too much. He trails Schneider by 50.5 to 49.5 percent with 99 of precincts reporting, and has conceded the race.

The suburban Chicago district has long leaned Democratic; Sen. Mark KirkMark Steven KirkThis week: Trump heads to Capitol Hill Trump attending Senate GOP lunch Tuesday High stakes as Trump heads to Hill MORE (R-Ill.) had a number of tough races there during his time in the House. Dold narrowly won the seat in 2010 during the GOP wave, and was a top Democratic target in redistricting, when ticket-splitting voters were replaced with more reliably Democratic votes. President Obama won 63 percent of the district's votes four years ago.

Dold becomes the fourth House incumbent to fall in Illinois, partly due to a Democratic gerrymander. Illinois has been House Democrats' biggest bright spot on Election Night.