Rick Perry belongs to the last group, Mitt Romney to the middle one. Jon Huntsman was probably the only major Republican presidential hopeful in the first. Until Tuesday.

In August, Huntsman famously tweeted: “To be clear. I believe in evolution and trust scientists on global warming. Call me crazy.”

But on Tuesday at the Heritage Foundation, Huntsman said, “The scientific community owes us more in terms of a better description of explanation about what might lie beneath all of this. But there’s not information right now to formulate policies in terms of addressing it over all, primarily because it’s a global issue.” He also cited “questions about the validity of the science evidenced by one university in Scotland recently.”

And then, puzzlingly: “Do I defer to science and those who happen to do this for a living? Yeah, I do, as I do on issues like cancer, for example.”

Confused? A spokesman “clarifies”: “He trusts the body of science on global warming, but there’s not global consensus, and we can't disarm or hurt our job creators since this is a global problem.”

No global consensus? There’s actually an explicit, written global consensus on enough of the science to motivate action, achieved during the Bush administration, no less — a huge report produced at the UN’s Intergovernmental Panel on Climate Change that member governments endorsed in 2007. There’s less agreement on constructing policy to respond, but that’s what policymakers such as Huntsman owe us, not scientists.

Aside from being a clouded criticism of climate science, Huntsman’s latest take has a whiff of that deepest of political sins: flip-floppery. Yet the governor’s new lack of clarity isn't exactly a repudiation of his old stance. It's just a poorly executed move toward the second GOP position on global warming — under which the likes of Huntsman and Romney can still signal that they are pro-science, just not quite so much.

A colleague of mine quipped that the big news here is Huntsman is now running for the GOP nomination. This is possible confirmation that, in order to be anything like a viable candidate in this year’s Republican primary, you have to be at least that second type of Republican. A candidate can argue against particular carbon-cutting policies regardless of which type he is; criticizing at least parts of the science seems to be necessary, too, even if it’s in a way that doesn’t totally rule out taking global warming seriously later. That’s better than pulling a full Rick Perry, but it’s still pretty bad for policy. The right should be proposing economically efficient solutions, instead of largely leaving the policy development to the Democrats.

The news isn’t, though, that Huntsman has suddenly sullied his heretofore pristine political virtue. He lost that in September, when he released a budget proposal that bought heavily into the GOP fantasy that taxes can be drastically reduced for high earners as America copes with rising health-care costs and retiring the boomers. Given how far right the other candidates are, Huntsman still looks much more sensible. But his virtue was already diminished. Now, more so.