"They're the ones that, with the encouragement of Senator Obama and his cronies and his friends in Washington, that went out and made all these risky loans, gave them to people that could never afford to pay back," McCain said.
Obama responded: "I've got to correct a little bit of Senator McCain's history, not surprisingly. ... In fact, Senator McCain's campaign chairman's firm was a lobbyist on behalf of Fannie Mae, not me."
McCain campaign manager Rick Davis has a stake in a Washington lobbying firm that received thousands of dollars a month from Freddie Mac until recently.
Davis is one of the many figures in both campaigns and near them who have been targeted as reasons why each should not be supported. As they head back on the road Wednesday, both campaigns say those associations would again be highlighted.
McCain running mate Sarah Palin has questioned Obama's ties to William Ayers, who 40 years ago was a member of the Weather Underground, a radical group that claimed responsibility for a series of bombings. Obama had a limited relationship with Ayers, who lives in the same neighborhood and teaches at the University of Illinois at Chicago.
Democrats have criticized McCain for his role in a 1980s banking scandal. He was one of five senators who had accepted contributions from Charles Keating Jr., a real estate speculator and savings and loan owner. Keating's institution failed and cost many investors in uninsured financial products their life savings.
Neither figure came up during Tuesday's debate. Nor did either candidate call the other a liar, a familiar charge in this contentious campaign.
The closest: "You know, Senator McCain, I think the Straight Talk Express lost a wheel on that one," Obama said.
During a discussion of an energy bill McCain offered up a two-word phrase that drew a quick reaction from the Obama campaign.
"You know who voted for it? You might never know. That one," McCain said, pointing at his opponent.
Obama campaign manager David Plouffe said after the debate, "John McCain was all over the map on the issues, and he is so angry about the state of his campaign that he referred to Barack Obama as 'that one' -- last time he couldn't look at Senator Obama, this time he couldn't say his name."
McCain also suggested some evasiveness on Obama's part: "Nailing down Senator Obama's various tax proposals is like nailing Jell-O to the wall. There has been five or six of them and if you wait long enough, there will probably be another one."
In one pointed confrontation on foreign policy, Obama bluntly challenged McCain's steadiness. "This is a guy who sang 'bomb, bomb, bomb Iran,' who called for the annihilation of North Korea -- that I don't think is an example of speaking softly."
That came in response to McCain's accusation that Obama had threatened to invade Pakistan.
McCain said his rival "was wrong about Iraq and the surge. He was wrong about Russia when they committed aggression against Georgia. And in his short career he does not understand our national security challenges. We don't have time for on-the-job training."
Obama countered with a trace of sarcasm that he didn't understand some things -- like how the United States could face the challenge it does in Afghanistan after spending years and hundreds of billions of dollars in Iraq.
The debate at Belmont University was the second of three between the two rivals, and the only one to feature a format in which voters seated a few feet away posed questions to the candidates.
The audience was selected by Gallup, the polling organization, and was split three ways among voters leaning toward McCain, those leaning toward Obama and those undecided.
Tom Brokaw of NBC, the moderator, screened their questions and also chose others that had been submitted online.