It seems like President Obama was looking past the debate, to more pressing matters.
What could have been more important to President Obama, than this debate with an empty suit?
Tensions between Syria and Turkey have escalated.
Fast forward to the Day of the First Presidential Debate. While the Very Important People were focused on President Obama's verbal joust with the empty suit, critically important events were occurring out of focus on the other side of the world:
Turkish armed forces have launched artillery attacks on a Syrian area near its border in response to a [Syrian] mortar attack which killed five members of the same family in southeastern Turkey.President Obama is almost certainly more concerned and focused on the implications if Turkey and Syria get into a full blown war. If Turkey invokes NATO Article 5, then NATO is at war with Syria. How much will it damage relations with Russia?
The Russians will almost certainly not go to war against NATO; but Assad is their only close ally in the Middle East. If Russia lets him go (without a fight), then it will signal a final transformation of Russia's Middle Eastern policy into one that is more aligned with the West. That would appear to be Russia's most rational course of action. There is a very good chance that Russia will follow the rational course:
Russian Foreign Minister Sergei Lavrov urged Syria on Thursday to state publicly that a mortar bomb attack on the Turkish border was accidental and would not be repeated, RIA Novosti news agency said....but Iran is the wild card. If NATO goes to war with Syria, there is a chance that Iran would become involved. From the Obama Administration's point of view, that cannot be allowed to happen. If NATO ends up in a shooting war with Iran, then all hell can break loose; because the Iranian leadership will be tempted to use the same gambit that the Iraqi leadership used in the First Gulf War: widen the war by attacking Israel. The Iraqi gambit failed, because Israel did not retaliate. But that gambit is much more likely to succeed now, because Netanyahu would almost surely use an Iranian attack as a pretext for attacking the Iranian nuclear program.
So if President Obama was off his game during the debate, it was because he had more pressing matters on his mind: avoiding a war in the Middle East that involves NATO, Syria, Iran and Israel. It's easy to see why that would be more important to him, than winning an argument with an empty suit.