This video of Rick Santorum showcases a fantastic body language example of the transition from mild anger to moderate-severe levels of anger (rage). Notice how the Republican Presidential hopeful's eyelids at first (with milder anger) grow closer together - into what some will call a "squint" configuration (think Clint Eastwood in "The Good, the Bad and the Ugly" - Clint is famous for this "look"). A few seconds later however, Santorum's eyes appear larger as his lids open up and his anger grows. This lid opening exposes more of the "whites of the eyes" (sclera) and is highly characteristic for moderate to severe degrees of anger. This is most notable at the 1:07 - 1:08 mark and again at 1:12 -1:17 and here it is considerably more prominent in Santorum's Left eye. There also is a large amount of mid-face tightening as well as thinning of Rick's upper lip. This is a classic anger cluster. When these nonverbals are accompanied by the hand gestures of finger pointing with arm-hand chopping, there is a significantly increased chance of physical altercation. In many other settings, without family members and cameras looking on, being in the national spotlight, etc. this probably would have occurred.
Santorum's use of "...come on man..." towards the beginning of this encounter was a form of verbally withdrawing his sword and attempting to apologize for his profanity. But after a short lull, his anger re-escalates. A very brief (microexpression) of rage occurs again at about the 1:54 mark.
It is interesting to note the gentleman to Santorum's left during this episode (wearing a pink and purple stripped tie). Probably a senior campaign assistant, his Inward Lip Roll" (ILR) was a nonverbal cue to us that he was, from a surrogate-empathy point-of-view, fruitlessly trying to control Santorum's temper. An Inward Lip Roll is a signal that our psyche is trying to control an outward display of negative emotion. This campaign manager was, for a moment, trying to prevent Santorum's anger from escalating - much like a fan contorts his body in an effort to "help" a player on the field to make a catch.