There is zero evidence to support your assertion that Romney was ahead after the first debate. His performance demonstrated that it was actually a contested election. But he was never ahead.
Well, if one is to believe any of the polls that came out in the next couple of weeks after the first debate, then, Romney was definitely ahead in the better known polls, like Rasmussen and Gallup.
I still maintain that, Romney could have won if he had gone for the knockout after the first debate.