McCain gingerly returned fire, reframing most disputes as a challenge to Obama’s aptitude. From assessing the surge to the merits of meeting with the leaders of hostile nations, McCain tried to cut Obama down by saying the young Senator did “not understand” the issues enough to reach a wise position. “[Obama] doesn’t understand that Russia committed serious aggression against Georgia,” said McCain, in a typical line knocking Obama for exhibiting “naivite” on foreign affairs. McCain sounded confident and somber throughout the foreign policy discussions, which dominated the night after an opening exchange on the financial crisis and federal spending.

The mood here at the debate site — admittedly irrelevant compared to the opinions of the TV audience at home — was measured, even bored, throughout much of the evening. Unlike other major debates, there was no singular exchange, be it angry, humorous or otherwise, that the press seized on to define the night.

I think the most striking exchange came near the closing, in response to Jim Lehrer’s expansive question about the prospect of another 9/11-level attack on the U.S. Obama advocated a return to American principles and human rights to restore the nation’s standing in the world, and then he proactively complimented McCain for fighting the use of torture. (Nevermind that McCain interfered with recent legislative efforts to ban torture by all U.S. government officials.) McCain did not respond in kind — instead he launched another talking point salvo at Obama, chastizing him for failing to “understand” the nature of the threats facing the U.S. It was an exchange that could leave viewers thinking McCain was ungracious, unrelenting or even tough, depending on how well he wears after 90 minutes of contemptously engaging his opponent.

Obama also added that he hopes “John McCain shows up” to tonight’s debate. Asked whether he will push back against the debate’s foreign policy focus, Obama said he would absolutely raise the financial crisis.

“With this looming in the horizon — this has an effect all across the globe. And one of the arguments that I’ve consistently made in this campaign is we can’t be strong abroad if we’re not strong at home. If we are spending 10 billion dollars a month in Iraq when they have a 79 billion dollar surplus,” he continued, “that just does not make for a safe and secure America.” Obama stressed that Iraq and its economic impact was a “fundamental” disagreement that he has with McCain, which merits a “debate format.” “We’re only talking about 90 minutes here,” he added, “I think that a president has to be able to do more than one thing at a time.”

If McCain bails on tonight’s debate, that is probably the line the Obama camp could use to hammer the absence. While McCain claims his presence is essential in Washington on Friday night, Obama could argue it’s another shortcoming that shows McCain is not well-equipped to handle the complex challenges of the modern presidency.