The following photos of French President Nicolas Sarkozy are relatively similar with respect to his mouth appearance - to the unobservant. But it is very important not to "lump" nonverbals together. I want to take this opportunity "thin slice" and contrast these expressions and their underlying emotions.
In this first image of Sarkozy we see deliberate and theatrical doubt displayed. When this extreme mouth configuration is shown, especially with the unilateral eyebrow and forehead contracture (as Sarkozy is doing on HIS right) there conscious and deliberate doubt present. Politicians often use this extreme lower lip "pout" and the "skeptical eyebrow" to telegraph their (often feigned) disbelief. It's melodramatic - but it's the nature of the political beast.
In this second photo of President Sarkozy, we see an "Inward Lip Roll" - in which the lips are being "gently bitten" (compressed) by the teeth. This is highly consistent with significant anxiety. Depending on the other nonverbals it is clustered with, the ILR can also be a signal of attempting to control and/or suppress other negative emotions - such as anger, fear, etc.
In this third image of the French President, he shows us what some refer to as the "Miserable Smile" (Ekman). Incredibly, even though this is an "upside down smile" - in the moment this body language is displayed, the person will believe they're making a slight smile. This is a fantastic example of just how unaware we all are of our emotional displays - particularly in the midst of negative emotions. In this variation of the inward lip roll, the lips stay in front of the teeth (rather than "gently bitten" by them as shown in the second image). His gaze is up and to his left, indicating he is probably visually recalling an event. This Body Language cluster strongly indicates Nicholas is experiencing the emotion of regret.
In this forth photo, we see a mouth expression consistent more with anger. The lips are visible (unlike the the second and third examples) but are stretched very thin in a classic (but misinterpreted by most) anger expression. The partially closed eyelids in this cluster-context are highly consistent with contempt-arrogance. President Sarkozy is experiencing anger-contempt in this moment.