If the Romney’s staff had a list of zingers for the debate, I suspect that “trickle down government” had to be on the list. It sounded remarkably fresh but familiar so I decided to look it up. “CrushingQuiet” said in the comments,
George H.W. Bush first used "trickle down government" in the ’92 debates: http://www.youtube.com/watch?v=Jg9qB_BIjWY&feature=related
I have not found the source for George H. W. Bush. Here is the video clip of Romney explaining the context of “trickle down government”, Romney coins trickle down government » The Right Scoop.