The turning point in Sen. Rick Santorum’s surprisingly successful primary campaign arrived during a January debate in Florida, where Santorum underscored Mitt Romney’s vulnerability on the healthcare issue:

Think about what that means going up against Barack Obama, who, you are going to claim, “Well, top-down government-run medicine at the federal level doesn’t work work and we should repeal it,” and he’s going to say, “Wait a minute, Governor. You just said that top-down government-run medicine in Massachusetts works well.” Folks, we can’t give this issue away in this election. It is about fundamental freedom… Those are not the clear contrasts we need if we’re going to defeat Barack Obama…

As Business Insider’s Grace Wyler noted at the time, “Mitt Romney was finally forced to play some serious defense…”

The healthcare issue itself was tangential to Santorum’s rise; social conservatives’ discontent with Romney ran far deeper than that. But it was during exchange that Santorum gained traction and became the most credible Not-Romney.

At this stage of the general-election campaign, it’s worth asking: Was Santorum right? Does the nomination of Romney effectively “give away” the healthcare issue for Republicans?

For the answer to that question, well, just listen to Romney flailing (h/t Jonathan Chait):

Actually, the — chief justice, in his opinion, made it very clear that, at the state level — states have the power to put in place mandates. They don’t need to require them to be called taxes in order for them to be constitutional. And — and as a result, Massachusetts’ mandate was a mandate, was a penalty, was described that way by the legislature and by me. And so it stays as it was.

Sympathizers may object that the Chief Justice John Roberts put Romney in an awkward position by wiping out the federalism argument in favor of Massachusetts’ mandate — which is true as far as it goes. Yet Santorum’s broader point was that it should not have mattered how the Supreme Court ruled on Obamacare; a Republican who hadn’t been previously tainted would have been able to command the healthcare issue independently of any help or hindrance from the judiciary.

None of this is to say that healthcare has become an advantage for Democrats. Rather, it is to suggest the issue has a become a wash — a non-advantage for Republicans. In a close election, it seems to me that could prove quite significant.