He also cast doubts about the credentials of his upstart Democratic primary challenger, Greenwich businessman Ned Lamont.
The state's junior senator, at times combative, also attempted to paint the Aug. 8 primary as a choice between a veteran senator who helped save the submarine base in Groton versus a political unknown who last served as a Greenwich selectman a decade ago and can't make up his mind about the issues.
Lamont, meanwhile, tried to use the hour-long debate to introduce himself to primary voters and hammer home that he's the true Democrat in this race who will fight President Bush on key Democratic issues and truly represent the hopes and dreams of Connecticut voters.
"Ned Lamont seems just to be running against me based on my stand on one issue, Iraq, and he is distorting who I am and what I've done," Lieberman said in his opening statement.
"I know George Bush. I've worked against George Bush. I've even run against George Bush. But Ned, I'm not George Bush," Lieberman said. "So why don't you stop running against him and have the courage and honesty to run against me and the facts of my record."
Lamont stressed that he's loyal to the party, unlike Lieberman, who announced Monday that he will begin collecting signatures to petition his way onto the November ballot as an independent candidate should he lose the primary.
"Senator, this is not about anybody's career," Lamont said. "This is about the people."
Lieberman, 64, is running for a fourth-term. Just six years after being his party's nominee for the vice presidency, he has fallen into disfavor among some Democrats for his perceived closeness to President Bush and support for the war in Iraq.
The race has garnered national and international attention. The debate was televised by MSNBC and C-SPAN. About 50 reporters were on hand at the WVIT-TV studios Thursday night, ranging from the Times of London to the Christian Broadcasting Network.
Scott McLean, chairman of the political science department at Quinnipiac University, said he believed both candidates, especially Lamont, accomplished their respective goals in what may be the only debate of the primary race.
"I do think what this debate has done is it has solidified Ned Lamont. These types of situations only help the challenger," McLean said. "The bottom line is, Ned Lamont gained more from this debate. He went toe to toe. He gave as good as he got. He didn't make any huge mistakes."
McLean said Lieberman appeared to have made a decision not to play to his persona as a gentle, likable politician. Rather, he was aggressive with Lamont, using the rebuttal time to challenge the businessman. It was a marked difference from Lieberman's mild-mannered debate in 2000 against Vice President Dick Cheney.
"He's playing against character," McLean said. "Who knows how that might affect some dynamic of this race. I think in the end, Lamont had more to gain by just showing up and doing a decent job."
At one point, Lieberman questioned why Lamont has refused to turn over his state and federal tax returns to The Associated Press. Lieberman said given the ethics scandals in Washington, transparency is important for politicians. Lamont said he has provided reams of documents to comply with federal disclosure rules, but did not say why he won't hand over the returns.
Nancy DiNardo, the state Democratic chairwoman, said Lieberman gave Democrats a reason to vote him into office for another term.
"I think that it became very clear that Joe showed that he is a Democrat. He is, in fact, a candidate who can get Democrats elected in this upcoming election," she said.
Lieberman said he has opposed Bush on most of the major policy initiatives of his administration, from tax cuts for the rich to privatizing Social Security — something Lamont accused Lieberman of supporting.
Lamont said Lieberman has undercut the Democrats on key issues, such as providing universal health care and battling efforts to enact voucher programs in public schools.
But Lamont's biggest criticism of Lieberman was the war in Iraq, an issue that helped to invigorate Lamont's candidacy.
"We have 135,000 of our bravest troops stuck in the middle of a bloody civil war," he said. "And I say ... those who got us into this mess should be held accountable. Let's have the debate."
Lieberman, however, repeatedly accused Lamont of changing his position on Iraq and whether or not he supports a deadline for withdrawing troops — a criticism Lamont denied.
"You have an open-ended stay the course strategy," Lamont said.
"No way," said Lieberman, who opposes a deadline but hopes troop levels will drop by the end of the year.
In an interview on CNN's Larry King Live Thursday, President Bush said he was not going to weigh in on Lieberman's primary race and declined to say whether he would support Lieberman if he ran as an independent.
"First, the Democrats have to sort out who their nominee is going to be and that's going to be up to the Democrats. And the rest of it's hypothetical," the president said.
When pressed about his liking Lieberman, Mr. Bush responded, "You're trying to get me to give him a political kiss, which may be his death."
A Quinnipiac University Poll has shown Lamont's support among registered Democrats increasing from 19 percent in May to 32 percent in June. Lieberman's support in the same period fell from 65 percent to 57 percent.
But the same poll predicted Lieberman winning with 56 percent of the vote if he runs as an unaffiliated candidate, compared with 18 percent for Lamont and 8 percent for Republican Alan Schlesinger.