Watching Romney plot out his election strategy, to me, is like watching a novice chess player bumbling through his opening moves, casting his pieces brazenly across the board in a rushed stampede to capture as many pieces as possible, without any thought as to the position it leaves him in. When you consider the way the Romney campaign has grabbed the "you didn't build it" line and turned it into a major campaign issue, you'd think he'd just grabbed one of his opponent's pawns and marched around the room in triumph.
Consider where this leaves him. Now Obama gets to make his point again and again, explaining his vision for the role of government and how it fits into his policy agenda. That's not a weakness. They're not putting Obama in a position where he has to explain something embarrassing, or problematic, or even just something that won't resonate with the American people. They're "goading" him into advertising his strengths. Obama started this frame by bringing it up in the first place. It's his territory, and obviously he wants to go on talking about it.
Romney, on the other hand, is left with what? How does his frame of "we DID build it!" fit into his policy? How does he take this into a broader conversation about his vision for America? Obama goes up with an ad -- a positive, "here's my vision" ad -- explaining how we need to invest in infrastructure. What's Romney's "here's my vision ad" that he gets out of this? The implication here is not that the government is standing in the way of business -- even Romney isn't really making that point. The only point he's making is "look, I'm attacking Obama!"
To switch to the sports metaphor, the Romney campaign claims Obama is on the defense, but I think they may have just handed him the ball.