Come on. Romney is getting kid-glove treatment now and he can't handle the press. What do you think it is going to be like if he is the actual Republican nominee.
Attacks on Romney’s fortune will hurt him. However, the only thing those attacks promote is envy. Eventually, the average person will realize that envy is not a logical reason to vote against someone.
However, the attacks on Santorum will be based on fear. The media will attempt to label Santorum as anti-woman... back-alley abortions, etc. Fear will keep female voters from voting for Santorum.
Romney may have trouble battling those attacks, but there is nothing Santorum could say to assuage those fears once the media attaches them to him.