You've got a point there; Reagan was tied or behind Carter at this point, as I understand it.
On the other hand, by this time in 1980 Reagan had already gotten off at least a half-dozen one-liners that hit Carter right between the eyes and put him off balance. Has Romney said even one memorable thing at the expense of Obama?
Romney is ahead of Obama because Obama is so much worse than Carter ever was. Romney's ahead of Obama without even trying.
Reagan didn't coast to the Convention in 1980.
Reagan made his bones in the debate.