In one of the night's closest races, Republican Mark Kirk defeated Democrat Alexi Giannoulias for the Illinois Senate seat. 

The Republican victory could be seen as perhaps the most embarrassing loss for the Democrats. Illinois, a state formerly thought of as a lock for Democrats, is where President Barack Obama served as senator before his election in 2008.

“Putting presidential prestige on the line,” Obama spent time in his hometown of Chicago on Oct. 7, campaigning for Giannoulias

The visit drew criticism and ridicule from Republicans.

State Republican chairman Pat Brady said, “If they have to bring in this kind of horsepower in a state like Illinois, which has been blue for a while, then the party’s in trouble.”

The New York Times’ Five Thirty Eight blog run by well-known statistician Nate Silver showed Kirk with a 68.7 percent chance of winning the seat as of Monday night.