In this video, Jay Carney, the White House Press Secretary, avoids commenting directly on the specifics of Mitt Romney's recent visits to the U.K., Israel and Poland - only in a very general way. While Mr. Carney did display two microexpressions of contempt at the 0:17 and 0:19 marks, there is another particularly interesting nonverbal displayed at the 0:39 second mark which should capture our interest - a mild-moderate lip purse.
Pursing of one's lips indicates that there is a disagreement occurring - here between Mr. Carney and what he thinks Mitt should have said/done compared to what Romney actually did. When is a lip purse present, there is a great disparity between what is being said and what is being thought (e.g. They may voice little or no disagreement, but they are thinking a much greater level of disagreement). It is also a signal that the purser has an alternative thought, plan, idea, etc. to what is being done, proposed, suggested by the other party - and that he believes his plan/idea is superior. A lip purser also believes he is a relative-alpha vs. whomever he is interacting with - thus he believes he has the power, resources, money to pull off his plan (People who perceive themselves to be relative betas don't display this body language). Moreover, he won't be sharing his idea with you - so get ready for an "end-run" and have your plan B (and plan C) ready.
In summary, a lip purse is a signal of clandestine disagreement and/or plans displayed from a relative alpha.