As many people who play poker know, people have certain quirks when they're bluffing. Some people tug on an ear, others smile, some scratch their head, knee, etc. Some get a stupid smirk. Other just play it cool, unusually cool. The question for a poker player looking for an edge is getting a feel for the other guy's "tell". The things about tells, these subconscious projections of our thought processes, is that they are involuntary. One of my past jobs was developing an online poker application, and in the research phase I studied poker players. One of my business partners makes a considerable portion of his income exploiting tells and drunken bravado, and once you learn to pick up on those signals, gambling becomes less of a gamble.
So what does this have to do with John McCain:
Watching that video, I noticed something about his left eye, every time he bends the truth, dissembles, or just outright lies. His left eye starts twitching more than his normal excessive blinking. McCain then looks down, in a rather sheepish fashion, and looks away from the interviewer breaking eye contact. This combination of nervous tick and classic avoidance behavior are both strong "tells" for John McCain.
I'm curious to see what other people could find going through the hundreds of hours of John McCain speaking on video. If one were to do a complete study of just his one-on-one interviews alone, just noting what is said and his body language, you'd get a better feel for how truthful he feels he's being. For such a "straight shooter", his body language gives his prevarications away.
Now Obama has a tell too. In fact he has several mannerisms which give away when he's stalling for time, trying to parse a statement, or just crafting a half truth. Watch how he touches his face on occasion, when a statement or comment disturbs him. Compared to McCain, however, Obama has much better control of his body language, and I wouldn't doubt that is in large part due to his actually speaking from the heart more often than not.
What tells can you find?