Both Jonathan Chait and Jonathan Cohn today noted the utter incompetence of Mitt Romney’s GOP rivals when it comes to basic opposition research, as shown by their failure to dig up two 2009 statements in which Romney supported a national individual health insurance mandate. These statements are completely at odds with Romney’s claim throughout this campaign that he has never backed a national individual mandate, but rather simply thought it appropriate for the people of his own state. Yet Mssrs. Santorum, Gingrich et al apparently could not bother to dig up the statements, which were contained in two very obscure corners: a USA Today column and Meet the Press appearance.

But I’ve been puzzling over another oversight by Romney’s opponents as we head into Super Tuesday: their total failure to make anything of Romney’s blatant flip-flop on the matter of the referendum over Ohio’s new law to restrict collective bargaining by public employee unions. Remember this one? In late October, Romney came to Cincinnati for a fundraiser and while in town visited a Republican phone bank where volunteers were making calls in support of the new law, the number-one priority of Gov. John Kasich. Yet when asked about the law at the phone bank, Romney ducked. “I’m not saying anything one way or the other about the two ballot issues,” he said. “But I am supportive of the Republican party’s efforts here.” Pressed by reporters, Romney refused to budge. “I am not speaking about the particular ballot issues,” he said, according to CNN. “Those are up to the people of Ohio. But I certainly support the efforts of the governor to reign in the scale of government. I am not terribly familiar with the two ballot initiatives. But I am certainly supportive of the Republican Party’s efforts here.”

Ohio Republicans were dismayed. How could Romney claim no knowledge of a major anti-union law that had dominated national headlines—even as he was visiting a phone bank making calls in favor of that very law? (It turned out he had also sent a Facebook message in support of the law a few months earlier.) “I suppose he’s trying to be cautious,” Mark Munroe, the GOP chairman in Mahoning County, told me at the time. Realizing the damage he’d done, Romney flipped the following day, telling reporters at a stop in Virginia “I fully support” the new law and “I’m sorry if I created any confusion there.” But the bad feeling lingered. Two weeks later, the law went down to resounding defeat, just the result that Romney was clearly anticipating as he tried to edge away from it even as he was showing up for a photo op at the phone bank.

This episode, you would think, might be something that Rick Santorum, Romney’s main rival in Ohio, might want to remind Republican primary voters about, especially as Romney is now trying to tar Santorum as insufficiently anti-union. But I can find no trace of Santorum doing so, on the trail or in his ads. (If I missed something, let me know.) Maybe Santorum figures that the law was so unpopular that trying to bring up Romney’s ambivalence about it might not be effective even among GOP voters, but that’s dubious to me—it seems that one could still craft an attack around Romney’s transparent expedience on the issue. I realize that Santorum has far fewer resources at his disposal, but really, this is kind of basic. Mitt Romney has to be asking himself, a la Jon Lovitz’s Mike Dukakis, how it is that he’s in a tight race with this guy. And he also has to be wondering what it’s going to be like when he’s up against a campaign operation that doesn’t miss these hanging curveballs.