Caveat: The study comes from Think Progress. But in case you’re inclined to doubt it because of its provenance, note that The Corner’s Patrick Brennan also reviewed transcripts from the last seven debates dating back to January 7 and found just one instance of Paul criticizing Romney — and that criticism was brief and mild.

Out: Conspiracy theories advanced by Ron Paul. In: Conspiracy theories involving Ron Paul.

While Paul has freely attacked Romney’s top rivals, he has never once attacked Romney…

Paul has gone beyond merely refraining from attacks. He has actively defended Romney on some of his biggest vulnerabilities…

Paul has also run advertisements attacking Romney’s key rivals at critical times. He ran hundreds of thousands of dollars in brutally negative ads attacking Gingrich in Iowa. Paul now is using his scarce funds on a television ad attacking Rick Santorum in Michigan, a key state where Paul is a non-factor.

TP’s tally of attacks by RP at the debates: 22 on Santorum, eight on Gingrich, four on Perry, four on Cain, one on Bachmann, and a big fat doughnut on Mitt. I can understand why he’d be drawn into slugfests with Santorum, who, as an extremely hawkish social con, is furthest away from Paul on the ideological spectrum within field. But Romney’s a natural Paul enemy too: He’s an establishment favorite, he paved the way for universal health care with his Massachusetts program, he’s considerably more hawkish than Paul, he has pro-choice roots, etc etc etc. Plus, insofar as he’s the consummate flip-flopper, he’s the anti-Paul; RP could have run a withering campaign against him emphasizing how likely Romney will be as president to shift with the political winds, especially vis-a-vis Paul himself. In fact, if you’d asked me before the debates began whom Paul would spend most of his time attacking, I would have guessed Mitt. What better way for a principled insurgent candidate to gain traction with the conservative base than by beating up repeatedly on a widely distrusted centrist for his betrayals of the cause? And yet … nothing.

I don’t think they’re coordinating, though — or at least, not formally. Paul’s advisors have been candid in interviews in explaining that his goal in running this time is to pile up delegates and gain some influence at the convention, either in terms of input into the party’s official 2012 platform or a primetime speaking gig or both. That being so, it’s only logical that they’d go easy on Romney. He was and is the likely nominee; the more helpful they are to him, the less resistance there’ll be to a convention role for the Paul family, especially since Romney will be nervous about alienated libertarians staying home if he freezes Paul out. RP tried running against the rest of the field in 2008 and got nothing from the establishment as thanks. This time, he’s taking a different tack. It’s working.