Well, embrace the most unconstitutional part of Obamacare; embrace the individual mandate.
Here's the relevant excerpt of Romney's piece, h/t Red State:
Our experience also demonstrates that getting every citizen insured doesn't have to break the bank. First, we established incentives for those who were uninsured to buy insurance. Using tax penalties, as we did, or tax credits, as others have proposed, encourages "free riders" to take responsibility for themselves rather than pass their medical costs on to others. This doesn't cost the government a single dollar. Second, we helped pay for our new program by ending an old one — something government should do more often. The federal government sends an estimated $42 billion to hospitals that care for the poor: Use those funds instead to help the poor buy private insurance, as we did.Again, the single most defining issue of Barack Obama's agenda in his first term was Obamacare. Romney's debate quiver will be out of arrows on this issue. Not only was his state's health care plan the blueprint for Obamacare but whenever the issue comes up, Obama will be able to snarkily say, "Tell me again, Mitt, why is my health care law unconstitutional?" Regardless of Mitt's answer, Obama can whip out the aforementioned paragraph each time Romney attempts to say it's unconstitutional. If Mitt stands by the position, Obama will be able to assert that Romneycare is unconstitutional, save for the tenth amendment argument.
Even then, Romney advocated Obama go against the Constitution... in 2009 (assuming his position now is that Obamacare is unconstitutional).
As the proverbial cherry on top, check out this montage of Mitt Romney over the last few years. Stick with it though and take note of how he says during a 2008 campaign debate that he supports mandates. Then candidate Fred Thompson calls Romney on it and said, "I didn't think you'd admit that."
h/t Hot Air: