Republican businessman Robert Dold has won the state's only open congressional seat by narrowly defeating three-time Democratic candidate Dan Seals.
With 94 percent of precincts reporting on Tuesday, Dold had 51 percent of the votes, compared with Seals' 49 percent. The race was closely watched and means Illinois now has a Republican majority congressional delegation for the first time in seven years.
Dold is the owner of a suburban Chicago pest control company. The 10th congressional district stretches north of Chicago. It has been largely Republican but had recently been trending Democratic.
Five-term Republican Congressman Mark Kirk gave up the seat and won President Barack Obama's old Senate seat on Tuesday.