"I'm saying he is less prepared than McCain," Lieberman said.
But what about Sarah Palin?
Is she ready?
"If, God forbid, an accident occurs or something of that kind?" Lieberman said. "Um, she'll be ready. You know, she's had executive experience. She's smart and she will have had on-the-job training."
Lieberman offered that faint praise of Obama and Palin in a contentious conference call with four Connecticut reporters about the recent tone of the McCain campaign.
"You guys are going down a road, you have contributed to the demeaning of our politics by this kind of focus," Lieberman said. "I mean, give me a break. Have any of you been out listening to me?"
Lieberman, a self-proclaimed "independent Democrat" who was chosen by McCain to make the case against Obama at the Republican National Convention in early September, said his comments have been within bounds.
"When I go out, I say, 'I have a lot of respect for Sen. Obama. He's bright. He's eloquent.' Someday, I might even support him for president, but now in the midst of this series of crises, John McCain is simply so much better prepared that that's who I am proud to support," Lieberman said.
Lieberman spoke from his home in Stamford after campaigning Thursday for the Republican nominee in New Hampshire.
On Sunday, he flies to Florida for several days of campaigning in that crucial battleground state.
Lieberman said he felt no obligation to address comments by McCain and Palin questioning the patriotism of places in America that are not supportive of McCain.
"I am prepared to be held accountable for my own comments on the campaign trail," Lieberman said.
Palin apologized this week for suggesting that some regions were more American than others. She had praised small towns as "the real America" and "the pro-America areas of this great nation."
McCain called western Pennsylvania, where he is competitive with Obama, "the most God-loving, most patriotic part of America."
Lieberman laughed when asked if McCain was suggesting that states like Connecticut, where polls show Obama is far ahead, pale in their faith or patriotism.
"Connecticut has always seemed to me to be a God-loving state," Lieberman said.
Lieberman said that both sides are guilty of intemperate remarks and ads.
"This is campaigning," Lieberman said. "This is campaigning as maybe we all wish it were not, but it is. I would just say that there's a lot of accountability to go around on all sides here."
Lieberman said he has refrained from using a McCain campaign label for Obama's call for higher taxes on the wealthy — "socialism."
"I don't use the word 'socialism.' I just think it's mistaken economic policy," he said.
Lieberman said he favors a more progressive tax structure that would impose higher taxes on the wealthy, who have benefited from tax cuts during the Bush administration, but not with an approaching recession.
"I think it's wrong to raise any taxes now," he said.
Lieberman initially sidestepped a question about Palin's readiness to be president on day one.
"She's not going to have to be president from day one because McCain is going to be alive and well. I've been talking to actuaries and doctors," Lieberman said. "He can be expected to live to his mid-80s and probably longer."
When pressed about when she would be ready, Lieberman replied, "Well, let's hope she never has to be ready."
He laughed, then quickly added, "Because we hope McCain is elected and lives out his term."
Lieberman said his own prescription for McCain to overtake Obama is that he end his campaign with a positive message:
"It is simply that he is ready. He's been prepared by a lifetime of being tested, of working across party lines in the Congress to get things done, of being fearless."
"He is ready to be our president at this very difficult time," Lieberman said. "And Sen. Obama is not as ready. It's as direct as that."