Herman Cain has been a great subject lately for Body Language Analysis and this short video is particularly instructive. I cannot recall a potential Presidential Candidate ever giving a speech wearing sunglasses. In this context, it strongly demonstrates distancing and blocking behavior. Mr. Cain doesn't want to the audience to make eye contact with him. Given the accusations, his polling numbers and the fact he's about to quit the race - this not too surprising.
At the beginning of this video when Cain says, "I am at peace with my God" and, "I am at peace with my ....Wife", he uses what some call the "Finger Point-Hand Chop" (FPHC), (It is more than a bit intriguing that Mr. Cain stutter-pauses just prior to saying "...Wife"). His index finger is extended and pointing with the rest of the digits closed in a fist-like configuration with the added "wagging"/up-and-down motion of the entire hand/arm. In this context, he's using the FPHC to passionately drive home his point and this hand gesture is quite common in such settings - although very ill-advised. Virtually all people will feel threatened when this over-the-top aggressive gesture is directed their way. It is overly used by strong alpha personalities and/or those with narcissistic tendencies.
In some settings (but here not in this video of Mr. Cain), such as when one is being directly confronted regarding possible deception or during testimony - the FPHC is strongly correlated with lying. You may recall President Clinton using this same gesture when he was denying allegations concerning Ms. Monica Lewinsky (see: Change the person, time and circumstances a bit ....) - or when Raphael Palmeiro denied his use of anabolic steroids at his testimony before congress.
When he is speaking, Mr. Cain has a habit of moving his mouth and lips in a considerably asymmetrical fashion (he"speaks out of the side of his mouth"). Most everyone will correctly interpret this facial signal as one of insincerity. Those who use this facial-gesture, are attempting a form of "verbal-nonverbal" swagger. While it may have this effect in short, well-placed moments - Herman, and many others, dramatically overuse it. Search your memory, whenever this technique is being used in a movie - the actor, script and director are all clearly trying to send a similar message.
At the 0:55 mark, just after Cain says, "....I am suspending my Presidential Campaign .....", he briefly (although here longer in duration than a microexpression) displays a classic bitter-regret frown expression.
Throughout the the majority of this video, Herman Cain had a superimposed highly characteristic expression of emotional pain - a frown with the contraction of his central forehead. No doubt most anyone in his shoes would be wearing a similar expression. Last stop for the Cain train.