The photograph above shows the two candidates greeting each other at the beginning of last night's debate. Notice that Obama is looking at McCain, and McCain is looking at the audience. It is just a moment, but it was typical. Throughout the ninety minutes that followed, McCain refused to make eye contact with Obama, even as Obama sought eye contact with him.

This asymmetry in the two candidates' body language is turning into one of the mini-narrative threads that start to form in the days following a major debate. It's interesting on the surface - for the signals it sent to viewers about McCain's feelings about Obama - and also because of what it says about the two men's characters.

There are two theories emerging about why McCain couldn't look his opponent in the eye. One of them - the most intuitive one - is that he feels such utter contempt for Obama, this kid who has achieved nothing who dares to challenge his judgment on foreign policy, that he doesn't wish to show him the minimum respect that eye contact implies. This is of a piece with McCain's exasperated grimacing at Obama's answers and frequent uses of phrases like "what my opponent doesn't understand...".

The other, fascinatingly proposed here, is that McCain's refusal to look his opponent in the eye was a sign of fear, or at the very least, insecurity (I haven't studied the tapes but as I recall Obama found it hard to look Clinton in the eye during their debates, and I think he did find her a bit intimidating).

Whichever it is - perhaps it's a mixture of both - it is indicative of something about the two men's temperaments. Obama, a former professor, is by instinct and education a man who separates an argument from the person making it. He is comfortable with abstract argument, and perhaps a little uncomfortable when things get personal. McCain, however - as Eugene Robinson points out to Chris Matthews - tends to personalise arguments. Indeed, McCain's whole worldview is based on character; he doesn't really have much of a political philosophy. That's not all bad: it's why he's got a good record of bipartisanship as a legislator - if he likes the man, he will disregard the ideology. But it means he's not a great at discussing ideas - and if he doesn't like someone, he can't help but let it show.