The Democratic Senatorial Campaign Committee is up with a new spot attacking Rep. Mark Kirk (R-Ill.) in the race to fill President Obama's former Senate seat. 

The open-seat race would be a huge prize for Republicans if Kirk was able to top Democrat Alexi Giannoulias in November. The latest polling has the race in a dead heat. 

The DSCC ad marks the first spot from either national committee in the race, though the National Republican Senatorial Committee has already pledged $3.4 million in coordinated money for Kirk.   

The 30-second ad hits Kirk's July votes against the extension of unemployment benefits. "We've heard a lot about Mark Kirk's problems lately, but Kirk doesn't know much about ours," the ad says. "On unemployment, Kirk said, 'I've heard very little. I have a very high-income district.' " 

The Kirk campaign hit back against the ad quickly Tuesday labeling it "misleading." The campaign said Kirk has voted to extend unemployment benefits a total of six times and has said he would do so again as long as the extension doesn't add to the deficit. 

The campaign also pointed out that the Kirk quote the DSCC ad relied on came in 2008, "when unemployment stood at 5.5%." 

The DSCC is already spending aggressively in both Colorado and Pennsylvania. The committee has sunk more than $1.5 million into ad buys against Ken Buck in Colorado and more than $2.5 million opposing former Rep. Pat Toomey (R-Pa.). The committee is also spending in Delaware, where Democrat Chris Coons is now the prohibitive favorite thanks to Tea Party-backed Christine O'Donnell's GOP primary win, and in Missouri.    

The NRSC has spent more than half a million on TV buys in both Colorado and Kentucky, where Republican Rand Paul is in a tight race against Democrat Jack Conway. 

In response to the  DSCC's ad buy in Illinois, NRSC Communications Director Brian Walsh highlighted the financial commitment Republicans have already made to Kirk. "After they saw what happened to Broadway Bank investors and the Bright Start families, is it any wonder that national Democrats don't seem to trust Alexi Giannoulias with their money?" asked Walsh.

-Updated at 12:41 p.m.