This Santorum ad does double-duty—it spreads misinformation about Obamacare and manages to pin Mitt Romney to Barack Obama:

I wonder if Santorum knows he has nowhere to go from here? He has virtually no path to the nomination barring a catastrophe of some sort, which means he's just doing President Obama's work for him. Is it possible that, like Mike Huckabee in 2008, Santorum loathes Romney personally so much that he's willing to destroy his own political brand just to take Romney down? I think that's very likely.