This doesn't strike me as a really powerful push-back against the charge that the Affordable Care Act strongly resembles Romneycare:

Mr. Romney gave his standard response, saying that if he were elected president, he would work to repeal the health care law passed under President Obama and grant waivers allowing states to opt out of it. A few moments later, he introduced a new line when asked whether he had the strength to aggressively challenge Mr. Obama.
“He does me the great favor of saying that I was the inspiration of his plan. If that’s the case, why didn’t you call me?” Mr. Romney said. “Why didn’t you ask what was wrong? Why didn’t you ask if this was an experiment, what worked and what didn’t?”

Well, Obama did hire the economist who designed Romneycare to design his plan. Why should he have also asked Romney, given that Romney was positioning himself to run against Obama in 2012?

Meanwhile, David Frum has a clever observation about Romney's stiff attempts to play the demagogue:

Romney has a tic of inserting caveats into his campaign boilerplate. For example, he blisteringly attacked President Obama for canceling  the European missile defense program. Here was something the Russians wanted, and President Obama gave it away without getting anything in return. Yet Romney’s critique contained a clause to this effect, “Even if you wanted to cancel the program anyway…” Again and again, Romney would salt statements that his audience wanted to hear with little mental asterisks noting that maybe what they wanted to hear was not exactly accurate, or wise, or in accordance with his own private opinions. Ironically it is this unwillingness to do the full 100% pander that creates the impression of “inauthenticity.” A less honest man would seem more authentic, at least for the moment.