On the substance, there is virtually no difference between the bills. Well, OK, there are two differences. No. 1 is that Romney did not vastly expand Medicaid in constructing his bill. No. 2 is that Romney did not raise taxes to pay for his bill. Now, both of those differences sound like they reflect very well on Romney—he didn’t expand a big-government program that most people associate with poor folks and therefore do not like, and he didn’t raise taxes.

But why didn’t his bill do either of those things? It didn’t expand Medicaid, because governors have no right to expand Medicaid. And he didn’t raise taxes because—ready?—the federal government paid for about half of it ($385 million, largely in Medicaid money). And the federal government paid for about half of it largely because of the efforts of … Teddy Kennedy, Romney’s great ally in putting the bill through. Jon Gruber, the Massachusetts Institute of Technology health economist who worked on Romney’s bill, has said, with only slight exaggeration: “They’re the same fucking bill. He [Romney] just can’t have his cake and eat it too. He can try to draw distinctions and stuff, but he’s just lying. The only big difference is he didn’t have to pay for his. Because the federal government paid for it. Where at the federal level, we have to pay for it, so we have to raise taxes.”…

Santorum was right Thursday night. Nominating Romney is giving up the issue, especially if the Supreme Court upholds the mandate. Obama probably can’t win the argument, but if his campaign handles the issue artfully, he can plant doubts in conservative and swing voters’ minds about Romney’s actual beliefs on the matter, which will play strongly into what presumably will be a key Obama theme of Romney as the say-anything candidate. Obama should even use Pawlenty’s little portmanteau. After all, it’ll be no loss to him if voters think of the plans as similar; making conservatives gnash their teeth is the point.