He had his chance at the convention and he blew it. The RNC spent their time either on defense or discussing nice things that were largely irrelevant to the fact that we have an election going on. This allowed the Democrats to remain on full offense at their convention. The Democrats, not needing to defend Obama, spent most of their convention bashing the Republican party as a whole, effectively turning Romney into an incumbent. I don't think the word "Democrat" was mentioned once at the RNC.
What's really being lost in the bashing of the Romney campaign is that he's doing nothing to create a narrative on why we need to elect Republicans, not Democrats, to the House and Senate. Not only is he way behind on selling himself, he hasn't even begun to sell the down-ticket Republicans. All it takes is explaining how Democrat policy has been bad for this country, but they won't do it. I think they think they want to convince "Reagan Democrat" types to vote for them, so they think bashing "Democrats" will turn off those voters. Which is amazingly wrongheaded. The Democrat who will switch to vote for a Republican will only do so if he AGREES that his party is doing a bad job. He's not going to take bashing of Democrats in Washington as a personal attack against him.
Truth be told...most Pubbies would rather come out of the closet and admit to be Democrats!!!!!