(CNN) - Mark Kirk, the five-term congressman representing the northern Chicago suburbs, announced Monday he will seek the Republican nomination for Illinois' open U.S. Senate seat in 2010.
The seat was formally held by Barack Obama, and currently belongs to Sen. Roland Burris who has said he will not seek to defend it.
Kirk, a moderate Republican whose district leans Democrat, said in Monday's announcement speech that he is "not an ideologue or party partisan," according to the Chicago Tribune.
The National Republican Senatorial Committee quickly endorsed Kirk, calling him an "experienced leader."
Meanwhile, the Democratic Senatorial Campaign Committee was quick to tie Kirk to former President Bush's economic policies.
“Republicans are asking the people of Illinois to replace the President with the anti-President,” DSCC Communications Director Eric Schultz said. “Congressman Kirk supported the Bush economic approach that got us into this mess and is now standing in the way of President Obama’s solutions at every turn.”
On the Democratic side, candidates reportedly eyeing the seat include Illinois Treasurer Alexi Giannoulias, Chicago Urban League President Cheryle Jackson, and Chicago businessman Christopher Kennedy. Kennedy is the son of the late Sen. Robert F. Kennedy, D-New York.
Lisa Madigan, the current state attorney general widely believed to be a top candidate for the Democratic nomination, said earlier this month she would not run.
(Updated with DSCC comment)