Made the Audience Laugh
Using humor in a debate is often even more effective than simply making a good point. Not only does the candidates get across his/her point of view, they also increase their likability. Both New Gingrich and Herman Cain have helped themselves by making the audience laugh, albeit in a somewhat different fashion. Mitt Romney's numbers in this category may indicate that he is a more likable candidate than the media gives him credit for. It may be that if he gets to a general election, moderate swing voters will find him to quite affable.
It should also be noted the biggest laugh of the campaign probably came from Gary Johnson in the one major debate he was allowed to participate in. His line was "My next door neighbor's two dogs have created more shovel-ready jobs than this current administration."