Senate Majority Whip Dick Durbin (D-Ill.) will serve as campaign chairman of the Democrat looking to fill Illinois's other Senate seat.

Durbin, the second-ranking Democrat in the Senate, will head up state Treasurer Alexi Giannoulias's (D) campaign, the Associated Press reported Monday.

The high-profile help comes ahead of what's expected to be a tough campaign in the Prairie State's Senate race, where Giannoulias will face off against Rep. Mark Kirk (R-Ill.) this fall.

"We know we're going to be outspent," Durbin said. "We realize we're the underdogs to this onslaught of money."

Kirk and Giannoulias will run to succeed Sen. Roland Burris (D), who decided not to seek reelection because of the controversy surrounding his original appointment to the seat, which was held by Barack Obama before he had been elected president.

Kirk, a centrist Republican from the Chicago suburbs, is hoping to pick up a seat for the GOP in the Democratic-leaning state, which political analysts see as a toss-up for this fall.