Rick Santorum last night on Piers Morgan’s CNN show, slamming Mitt Romney for having supported the individual mandate at the federal level:

What I’d like to talk about, which is offensive, which is Governor Romney out there for almost a year telling the people in the Republican primary that he never advocated that Romneycare would be a federal model.

That he never advocated for an individual mandate, that government at the federal level require people to buy insurance, and now we find on several occasions, just in the past week, article after article, interview after interview, where Governor Romney did just that in 2009. Now, to me, that’s offensive.

For the — for someone to go out and deliberately misrepresent his record, what he did at a very critical time, when people were making decisions on the issue of health care, for him to go out and recommend that to President Obama and then tell the voters on debate after debate that he never did any such thing, not only is his policy bad, not only did he recommend the wrong policy for the country, that he didn’t tell the truth about what he did.

And to me, that’s something that should be a much bigger issue on, supposedly, the leading candidate in this race, on the most important issue that we’re going to be dealing with in this election.

Insofar as he’s criticizing Mitt Romney for lying about having supported the individual mandate, Rick Santorum is indisputably correct. Romney supported taking it national, and did so unambiguously.

Santorum is also right that Romney’s past support for the individual mandate will neutralize any possibility that Republicans will be able to take advantage of the issue in November (though it’s not clear they would have been able to anyway).

But to the extent that Santorum is shocked that this issue hasn’t been the undoing of Mitt Romney, he’s got nobody to blame but himself. Despite having been on the stage for 20 different debates with Romney, Santorum never once was able to pin Romney down on his lies and the simple reason is that his campaign team failed to do adequate research on Romney’s record.

But now that BuzzFeed has uncovered the evidence of Romney’s past support for the individual mandate, Santorum might have one last shot at taking the nomination away from Romney. His task is to convince Republicans that it would be suicide for them to nominate the father of Obamacare. Santorum’s problem is that Republicans probably also realize it would be even bigger suicide to nominate a guy who openly admits he doesn’t believe birth control is okay and promises to use the bully pulpit of the presidency to spread that message.

In all likelihood, Santorum won’t be successful. But even if he isn’t, you can bet this issue won’t go away. Mitt Romney has now staked his entire argument against Obamacare on a Tenth Amendment, states’ rights argument. But as recently as 2009, Romney didn’t accept that argument. He won’t be able to abandon it during the campaign, but he won’t be able to credibly defend it either. When he debates President Obama, Obama will make mincemeat out of him. Because unlike Rick Santorum, President Obama not only has a good opposition research team, but he knows how to use it.

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