Obama had noted that McCain didn't raise the issue "to my face" in their debate on Tuesday, but McCain told Gibson he did not raise the Ayers argument during the debate because "it didn't come up in the flow of conversation."
But McCain told Gibson he felt comfortable with the subject as a focus in the last days of the campaign.
"I think it's something that needs to be examined. Sen. Clinton said it should be examined during their primary and it never was," McCain said.
McCain, who has thus far resisted engaging in some of the political attacks more often seen from his surrogates or Republican vice presidential nominee Sarah Palin on the campaign trail, repeatedly hinged his first direct discussion of Ayers on Obama's primary rival, Sen. Hillary Clinton, D-N.Y.
"Sen. Clinton in their debates said that the American people didn't know enough about him, including his relationship with Mr. Ayers. That's what she said. And I agree with that," McCain said, rejecting the suggestion that Obama has been "thoroughly vetted" over the course of a near two-year battle for the White House.
"Does he have the experience and the knowledge and judgment and has he made the right decisions?" McCain asked in the Gibson interview, "and has he told -- been candid with the American people? I think that's important."
"They certainly know me," McCain added, in reference to the American public.
Obama has rejected such a premise.
"The notion that people don't know who I am is a little hard to swallow," Obama told Gibson on Wednesday, "I've been running for president for the last two years. I've campaigned in 49 states. Millions of people have heard me speak at length on every topic under the sun. I've been involved now in 25 debates, going on my 26th. And I've written two books which any -- everybody who reads them will say are about as honest a set of reflections by, at least, a politician as are out there."
Obama suggested the McCain campaign's turn toward personal attacks is an effort to avoid discussing the ailing economy.
"Sen. McCain's campaign has been focusing on me primarily because they don't want to focus on the economy. And they've said as much. I mean, you've had their spokespeople over the last couple of days say if we talk about the economic crisis, we lose," Obama said.
But the economy was a top priority for McCain as world markets continue to struggle despite passage of a historic, $700 billion economic rescue package by Congress.
"We are in a crisis of unprecedented proportions. And that's why I recommended strongly that we go out and have the Treasury buy up these bad mortgages, so and arrange it as they did during the Depression," McCain said, referring to a plan he proposed during the second presidential debate in Nashville on Tuesday.
"Sen. Clinton has recommended this," McCain said. "Buy up these mortgages. Let people have them in affordable payment levels. And put a floor on this continuing plummeting of housing -- of home prices. As long as that value continues down, I don't see a stabilization."
But McCain's plan has come under fire from both conservatives and the Obama campaign as one that rewards banks that knowingly provided the riskiest mortgages and bailing out irresponsible homeowners with the taxpayer's money.