11/03/2010 12:41 am ET Updated May 25, 2011

Mark Kirk Wins Illinois Senate Race, Defeating Democrat Alexi Giannoulias

Mark Kirk, the five-term Republican congressman from Chicago's north suburbs, has won his bid to fill Barack Obama's old Senate seat in Illinois.

Kirk defeats Democrat Alexi Giannoulias, the state treasurer who was hoping to keep the seat for his party. Though the race was very close, Giannoulias conceded late Tuesday. With 97 percent of precincts reporting, the Democrat trailed Kirk by about 83,000 votes.

In an unusual wrinkle to this race, Kirk also won the special election to serve the rest of President Obama's term in the Senate, in the seat currently held by Roland Burris. Kirk will be sworn in prior to January 20, 2011, when the rest of his incoming Senate class will take their oaths; instead, he'll replace Burris for the "lame-duck session" this winter. This could stymy Democrats' hopes to pass some last progressive legislation before the Republican tide rolls in.

Kirk won the Republican primary all but unopposed. Bucking the traditional pattern, Kirk has drifted away from his more moderate positions and toward a more conservative stance during the general election campaign, trying to attract the support of the newly energized Illinois right.

As a Congressman from a swing district, he was long a supporter of abortion rights and the environment; he voted for the House's ambitious cap-and-trade legislation, one of only eight Republicans to do so. But he repudiated that vote on the campaign trail, and voted for the controversial Stupak amendment to the healthcare reform bill while running for Senate as well, hoping to boost his bona fides with Tea Partiers and other Illinois conservatives who often derided him as a RINO (Republican In Name Only).

For his part, Giannoulias has been a strong supporter of the Democratic agenda from Day One. In a cycle where many Democrats actively ran away from the President and the party, Giannoulias embraced them, advocating for the stimulus and the healthcare reform bill and frequently appearing at rallies with President Obama and White House leaders. Alexi was banking on the state's Democratic base, and its continued affinity for a President who launched his political career here, to drive turnout and carry him to victory.

Tuesday night's results showed that calculation failed. Instead, Mark Kirk and the Republicans' repeated attacks on Giannoulias's character, coupled with a disgruntled, anti-Democrat electorate, brought an end to Giannoulias's Senate aspirations.

Kirk will join an energized class of freshman Republican Senators who will look to challenge President Obama and his Congressional Democrats on their more progressive policy aspirations. As results come pouring in from around the country, Kirk -- now officially the winner in a hotly contested toss-up race -- is one member of the class that Republicans must be thrilled to have along.