The main thing is that Rick Santorum showed himself to be a complete jerk:
1) He, like Perry, persistently interrupted Romney when it was Romney’s turn to talk. In both cases I appreciated Romney’s approach of being a stickler for the rules and largely drowning them out.
2) He “introduced himself” by telling his daughter that he loves her and he will see her soon. (She had surgery yesterday). Either he was using us to convey a message to his daughter (“I love you so much that I am willing to waste the time of millions of viewers to send a message to you”), or (more likely) he was using his daughter to convey a message to us (“I am a family man”). Either way, no good.
3) He uttered the sentence “The basic building block of a society is not an individual.”
Also Rick Perry showed himself to be a total jerk, primarily by accusing Romney of hiring illegal immigrants (via his lawn care company). I bet there are fewer than 1000 people in the country who would actually refrain from (knowingly) hiring illegal immigrants to do lawncare if they thought no one was watching.