Steele, for his part, battered Cardin on the congressman's plans for the war in Iraq.
A Washington Post poll put Cardin ahead by 11 percentage points, but the Cook Political Report changed the race from "lean Democratic" to toss up.
Cardin and Steele are vying for the open seat vacated by retiring Democratic Sen. Paul Sarbanes.
Much of the debate centered on the war, with "Meet the Press" moderator Tim Russert pressing each candidate to cement their position on how the United States should remove its troops from Iraq.
Steele labeled the war as "a mess that we need to fix" and called for the Bush administration to "put the pressure on the Iraq government and force them to own up their responsibility to take control of the situation on the ground." He also expressed his support of the plan proposed by Senate Armed Services Committee Chairman John Warner, R-Va., which calls for a re-evaluation of the situation in two to four months.
When asked by Russert, however, whether he would have voted against the war as Cardin did had he been in office in 2003, Steele responded, "I would think we'd still prosecute the war."
Cardin faced questioning from Steele about his plan, especially a report in the Baltimore Sun which quoted Cardin as saying that he would cut off funding for the war if the course in Iraq did not change.
"You're now saying that you don't want to fund the war, that when you get control of the Congress, your vote is going to be to de-fund our troops on the ground. That's your plan," said Steele.
"I would consider using the appropriation process, I will not support putting our troops at risk," responded Cardin. He said that his plan for Iraq would be to not set a timetable for the removal of troops, but to gradually redeploy troops and have the international community facilitate a diplomatic end to the conflict.
The rest of the debate focused on Steele and his affiliation with the ideologies of President Bush and the Republican Party. Cardin has tried, in advertisements and speeches, to attach Steele with President Bush's policies in a state where Democrats outnumber Republicans by a 2-1 ratio.
"Mr. Steele was recruited by the Bush administration," Cardin said during the televised appearance. "You look at what he's done. I'm concerned what he will bring to Washington. He supported the President in the war in Iraq, and still supports that decision today."
When asked about his commitment to the Republican Party, Steele said, "I'm going to evaluate every issue as it comes to me and where my party is wrong, I'm not standing with it, I'm not voting with it."
The differences between the candidates appeared again on the issue of stem cell research.
Actor Michael J. Fox, who has Parkinson's Disease, produced a campaign advertisement endorsing Cardin based on his support for embryonic stem cell research. The Steele campaign responded in an advertisement featuring Steele's sister, Monica Turner, who suffers from multiple sclerosis, and saying Steele supports stem cell research.
Steele said he was against embryonic stem cell research because he sees the embryos as a human life, but said he had to look further into the question of using embryos slated for disposal by fertility clinics by looking into their procedures in such cases.
"Would I forbid them from destroying embryos? Probably would like to look at that a little bit more closely. ... I don't know exactly how that mechanism is set up right now with respect to each clinic," said Steele.
Cardin presented himself as a strong advocate of stem cell research and again tried to label Steele as a Bush follower.
"I voted to override the president's veto, a bill that was bipartisan, worked so that we could advance embryonic stem cell research," said Cardin. "Mr. Steele supported the president's veto in that regard."
The candidates also faced off on confirming Supreme Court justices, affirmative action and abortion law.