Republican Mark Kirk, a five-time Congressman, narrowly defeated Democrat Alexi Giannoulias in the race for the Illinois Senate seat once held by President Obama. The race was one of the closest in the country.

Rep. Mark Kirk (Courtesy of Mark Kirk's Facebook page)

Kirk and Giannoulias wrapped up their campaigns in Chicago Tuesday morning before heading to the polls to vote.

Obama campaigned for Giannoulias, the state treasurer, in Chicago on Oct. 7. The president's visit drew much criticism 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."

Former President Clinton and Sen. John Kerry also campaigned for Giannoulias.

Crossroads GPS, a conservative group with ties to Karl Rove, spent $1 million on a series of ads against Giannoulias in early October, charging him with losing money for Illinois families.

The Democratic Senatorial Campaign Committee struck back later that month and ran an 30-second ad attacking Kirk's military record with less than two weeks before the election, sparking outrage from Republicans.