(CNN) - Illinois State Treasurer Alexi Giannoulias will officially jump into the 2010 race for U.S. Senate on Sunday.
Giannoulias will make his formal announcement in Chicago and the state capitol of Springfield, as he kicks off a three-day, seven-city swing,
according to his exploratory committee.
The seat was formally held by Barack Obama, who stepped down from the Senate in November following his victory in the presidential election. Sen. Roland Burris currently holds the office. Burris said earlier this summer that he will not run for a full term next year.
Republican Mark Kirk, the five-term congressman representing the northern Chicago suburbs, announced Monday he will seek the Republican nomination for the seat. Kirk, a moderate whose district leans Democratic, said in Monday's announcement speech that he is "not an ideologue or party partisan," according to the Chicago Tribune.
Besides Giannoulias, Democratic candidates reportedly eyeing the seat include Chicago Urban League President Cheryle Jackson and Chicago businessman Christopher Kennedy. Kennedy's father, the late Robert F. Kennedy, represented New York in the Senate. Illinois Attorney General Lisa Madigan, who was widely believed to be a top candidate for the Democratic nomination, said earlier this month she would not run.