Uh... well pretty much the whole thing. Shoot, even Ron Paul bitchslapped him on Abortion... and that was unexpected. Paul is against Abortion like Rick, but is NOT for Federal control of it, he believes it is a state issue and votes that way. Santorum barked up the wrong tree on that one for sure.
Best moments were here: http://www.youtube.com/watch?v=ZcYF5aNwUeI&feature=youtube_gdata_player EPIC smackdown.