One thing we can be sure of that will happen tonight in the Presidential debate is that Obama will lie. He will lie about the federal debt ("I inherited it"), he will lie about the economy ("we've created 5 million jobs"), he will lie about Fast and Furious ("it was started under Bush"), etc., etc. He will lie because he is a man who does not know the truth, and does not even believe in the concept of the truth. He believes in manipulating words to create demagogic effects (a) because he's a post-modern Marxist at his core, a la Saul Alinsky; and (b) because he's a narcissist who lives for the moment of adulation when people tell him what a great speaker he is.
I don't know if Romney will handle Obama's lies very well. Romney is a moral man who believes in God and believes in the truth. He's also a man who spent his life in business. As much as the businessman has been demonized in popular culture, the reality is that one thing you learn in business (and in the actual practice of law as opposed to the bullshit Obama did as a community organizer and "law professor") is that you can't lie. If you lie, you lose, because people in business have to trust you (just like the one thing you have to always maintain in court is your credibility in front of the judge and the jury). So he's not used to baldface liars, and particularly ones as slippery as Obama.
I also expect the media to go deeply in the tank for Obama in spinning his performance. When he lies, and Romney calls him on it, the media spin will be about how deftly Obama parried Romney's attacks, and how Romney didn't really lay a glove on him. They will talk about style rather than substance, in short.
This is a 2,000 plus year-old argument: Plato against the Sophists. Rhetoric against Truth.
I'm afraid we live in a world where Truth matters less and less.