During this recent interview in Israel, Mitt Romney describes his feelings regarding an aspect of campaign finance rules with which he voices a strong disagreement. At the 0:24 - 0:25 mark, he displays a facial "near-microexpression" of disgust (expression here is of slightly longer duration than is classically defined for microexpression, 0.04 to 0.50 seconds). Note his mid-face tightening (mustache area) with both nostrils flaring and dynamic contraction on the bridge of his nose. His head/neck also retracts slightly as well as a concomitant partial closure of his eyelids, an increase in the "crow's feet" and lowering of his eyebrows. His nasal-labial furrow also becomes more pronounced. Since Mr. Romney's verbal and his nonverbal message are congruent, his sincerity quotient his high on this issue.
When someone's words and body language are in disagreement however - always believe the body language.