Republican congressman Mark Kirk and Democratic state treasurer Alexi Giannoulias are fighting for an edge in the tight race with the election just two weeks away.
Everything was up for grabs in the debate - from the deficit to immigration to the character of the candidates.
Because of a recent Supreme Court case, the increasingly bitter race for the president's old Senate seat is being fueled by millions of dollars in money from outside the state of Illinois.
The debate format did allow the panel to illustrate some differences between the candidates who did their best to return to familiar negative claims about one another.
The Giannoulias family failed bank and Kirk's past embellishment of his military record came up within minutes of the debate's beginning.
"I misstated a part of my military record. It's a painful process. I learned a big lesson from that. I apologize to the people of Illinois. I then released all 21 years of my officer fitness reports," said Kirk.
"I'm very proud of the community bank that my father started 30 years ago. Let's be clear, no one has ever suggested the bank has ever done anything illegal, illicit or improper, never," said Giannoulias.
Then the candidates were asked about the issues. Kirk says he's still convinced the economic stimulus was an expensive mistake.
"The lasting legacy of the stimulus will be a near trillion dollar debt leveled on the financial future of our kids," said Kirk.
"Economists across the board will tell you that the Recovery Act helped stem the second Great Depression," said Giannoulias.
When asked if African-Americans were the targets of Congressman Kirk's voter integrity program the candidates took off the verbal gloves. And a question about the Dream Act -- to allow undocumented immigrant students or military members to remain in the country -- caused more sparks.
The candidates disagreed on the Supreme Court's recent Citizens United decision allowing corporations to make secret donations to groups that produce negative ads like many aired in Illinois this fall.
"He's bought and paid for by wall street firms which is why he voted for the bailouts of the biggest banks in the world proudly twice," said Giannoulias.
Kirk said he supports disclosure but opposes pending legislation to force the groups to disclose only their corporate donors.
"The Disclose Act, which is a very flawed piece of legislation Speaker Pelosi put forward, says that basically we should restrict the speech of corporations but not the speech of unions," said Kirk.
The outside money continues to flow into the race, the vast majority of it apparently spent by groups in support of Kirk. But he says Giannoulias is getting outside support from labor unions and left-leaning organizations who are also buying of television time. Experts say that this will undoubtedly be the biggest year for campaign spending in an Illinois U.S. Senate race.