Romney's argument keeps most Republicans at bay because it taps into their principled beliefs about states' rights, and is simple. Yet, it also implies he is either duplicitous or that he is against any and all federal legislation.
Rick Perry needed a big night and he didn't have one. Cain needed to push his message beyond the 9-9-9 plan but he couldn't do it. Romney needed to maintain the status quo -- that he managed, and then some.
Because this will be Mitt Romney's first debate appearance, political observers are going to be closely watching how intensely the others attack him and his positions, and how Romney responds to such attacks.