After years of bashing Obamacare and minimizing his involvement with health reform in Massachusetts, Romney presented his success at insuring 100% of children in Massachusetts as evidence of his empathy. While emphasizing his past achievement might help blunt the attacks over his 47% comments, it also emphasizes the amazingly narrow path he has to walk on health care. He has to pretty much admit that most of the elements of Obamacare are good, as most are similar to Romneycare, but follow that up with a federalism argument for why Obamacare itself is actually bad. So he'll turn off most conservatives with his support for mandates at the state level, but lose most liberals with his opposition to Obamacare.
Romney's forced into this position given his record as governor. He is the single worst Republican in the history of the party to attack Obama on health care.