"You said that we were going to be greeted as liberators. You were wrong. You said that there was no history of violence between Shia and Sunni. And you were wrong."
McCain sought to make use of an unpopular answer Obama gave in a July 2007 primary campaign debate when he said he would meet without preconditions with the leaders of certain nations hostile toward the United States during his first year in office, a position Hillary Clinton also tried to use to suggest that he is naive.
"So let me get this right. We sit down with Ahmadinejad, and he says, 'We're going to wipe Israel off the face of the Earth,' and we say, 'No, you're not.' Oh please," McCain said.
Obama responded by saying that he would meet with anyone if it helped the nation's security, but that advance staff work would be needed beforehand. "This is a mischaracterization of my position," he said.
For the most part, there was little warmth between the two opponents and neither man made a serious error that could damage his candidacy. There were almost no hints of humor and only an occasional tip of the hat to something positive the other has done. (Obama praised McCain's stance against torture.)
PBS moderator Jim Lehrer repeatedly tried to get each candidate to directly engage the other, with some success.
The first half of the debate was devoted almost entirely to the fiscal crisis on Wall Street and how the two men would vote on pending legislation in Washington, as well as how the matter was likely to affect the next president.
Both candidates offered lukewarm support for the bailout package, which is expected to cost about $700 billion. And both said they would like to see oversight, accountability and transparency to protect the taxpayer from supporting wealthy CEOs.
"This isn't the beginning of the end of this crisis," warned McCain. "This is the end of the beginning - if we come out with a package that will keep these institutions stable."
Obama quickly brought the issue around to ordinary Americans, which McCain later echoed, saying the government had to move swiftly and wisely.
"Although we've heard a lot about Wall Street, those of you on Main Street, I think, have been struggling for a while, and you recognize that this could have an impact on all sectors of the economy," Obama said. "And you're wondering: How's it going to affect me? How's it going to affect my job? How's it going to affect my house? How's it going to affect my retirement savings or my ability to send my children to college?"
They sparred on spending priorities, as well as the practice of earmarking pork-barrel projects for use at home.
Obama "has asked for $932 million of earmark pork-barrel spending, nearly a million dollars for every day that he's been in the United States Senate," McCain complained.
Responded Obama: "Let's be clear: Earmarks account for $18 billion in last year's budget. Senator McCain is proposing - and this is a fundamental difference between us - $300 billion in tax cuts to some of the wealthiest corporations and individuals in the country, $300 billion. Now $18 billion is important; $300 billion is really important."
The two presidential hopefuls are scheduled to debate twice more, at Belmont University in Nashville, Tenn., on Oct. 7 and at Hofstra University in Hempstead, N.Y., on Oct. 15. Vice presidential contenders Sarah Palin and Joe Biden are to square off in a single debate Thursday at Washington University in St. Louis.