“Big problems demand big change, and Alexi gets it,” Quigley said in a statement. “I’m proud to endorse Alexi Giannoulias to be our party’s candidate for the U.S. Senate.”

Quigley joins Reps. Phil Hare and Bill Foster, who had previously announced they are supporting the state treasurer in the race.

Giannoulias is currently the only credible Democrat running for President Barack Obama’s former Senate seat in 2010, but he is not expected to get a free ride in the primary. Chicago Urban League President Cheryle Jackson has opened an exploratory committee to look at running, and businessman Chris Kennedy (D) is expected to run as well.

Republicans are expected to coalesce behind Rep. Mark Kirk as their Senate nominee after Kirk officially announced he is running Monday.

Quigley is the newest Member of the Illinois delegation. He won a special election in April to succeed former Rep. Rahm Emanuel (D), who left the House to become White House chief of staff.

Hastert to Kick Off Campaign This Week

Attorney Ethan Hastert (R), the son of former Speaker Dennis Hastert (R-Ill.), got some fundraising help from his father’s political action committee this past quarter as he gears up to challenge Rep. Bill Foster (D).

Out of the $87,000 that he reported raising so far, Ethan Hastert received $10,000 from the elder Hastert’s Keep Our Mission PAC.

Ethan Hastert also received $5,000 from Rep. Aaron Schock’s (Ill.) leadership committee, GOP Generation Y Fund. Schock, who at 28 is the youngest Member of the House, will be the special guest at Hastert’s campaign kickoff reception this week.