Environment
It would be a full time job monitoring all of the partisan bias and factual-errors peddled by the New York Times. Consider yesterday's story, "Climate-change science makes for hot politics," in which the Times plays scientist and concludes:
Human activity, including the burning of fossil fuels, is pumping carbon dioxide and other greenhouse gases into the atmosphere and warming the planet.
As I write this, CNN's international broadcast is running a pre-Durbin UN climate change conference, shame-on-America special about global attempts to reduce carbon in order to fight climate change - and the science of man-made global warming, don't you know, is settled.
The Times can be excused for its ignorance of the immense damage done to global warming alarmists by both skeptics and their own revealed dishonesty and politicalization, since the Times rarely bothers to cover news harmful to one of their golden-calf platforms. The same is true for CNN and the whole lot of the derisively-labeled MSM.
At least, the Times reminds readers that Mitt Romney, Newt Gingrich, Jon Huntsman and the on-again (since he lost the presidential election) media doll John McCain have toed the liberal line and accepted the media narrative on global warming. The Times delights in reporting that Huntsman actually ridicules conservatives on the issue of global warming, having recently branded the GOP as "the anti-science party" and "a bunch of cranks," as well as tweeting, "I believe in evolution and trust scientists on global warming. Call me crazy." John Hinderaker at Power Line rights ponders why in the world this guy is running for president as a Republican.
Rick Perry and Michele Bachmann continue to strongly pronounce the science of global warming as bunk. While the Times' story is ostensibly about the GOP's political division on the issue, it doesn't even actually bother to quote Perry - but it does provides a link on the side of the webpage to "Rick Perry's made-up 'facts' about climate change." So the story continues the Times' proud tradition of fair and balanced news coverage.
This is just one of many issues which will separate Perry and Bachman from Romney in conservative circles. While climate change will not emerge as a hot topic in this election, it is a useful litmus test for conservative credentials and isn't an issue upon which conservatives should retreat.
Huntsman is Republican because he is Mormon and thus socially conservative.
The same might be true of Romney except that he is also a sort of business conservative.
But there is no real principle that can be developed which opposes or supports global warming. So it isn't an issue of principle.
It more or less is an issue of fact. At best it is a synthetic litmus test of conservative credentials. Synthetic in that it is derived mainly from business interests opposed to the consequences of policies that might deal with the issue.
By raising it to the level of a litmus test you guarantee that these buisiness interests continue conservative support. So it is more a question of packaging.
Huntsman and Romney aren't scientists, but they agree that man made climate change is real. They probably would still end up spending less money and effort combating global warming.
So you have 1 question which is a question of fact...is global warming real, and then a second question which is a question of policy...what can be done to combat it and at what cost.
The demise of "moderates" in the GOP stems from the fact it is easier to collect money if you stand fast at the level of answering questions of fact in such a way as to foreclose having to fight on questions of policy.
Huntsman calls this "anti-science" but in truth it is just "pro-mechanical economics", denying global warming is highly effective for never getting to the point of supporting or opposing on measures that deal with it.
Huntsman and Romney I think realize that if all of politics gets swallowed up by "pro-mechanical economics", we are in difficult times.
"It is a useful litmus test for conservative credentials" I suppose it is if you want to build a conservative that basically gives you an answer.
X,Y,Z is offered into evidence for global warming and the conservative litmus test spits out a summary judgement rulling against global warming.
X,Y,Z is offeted into evidence against global warming and the liberal litmus test spits out a summary judgement rulling in favor of global warming.
Our sythentic conservative and liberal created by operation of "pro-mechanical economics", obliterates the role of moderates, or those who might on the basis of evidence give out rullings which go against the conservative or liberal litmus test (economic packaging).
So I think both Romney and Huntsman don't want to be taking positions against the weight of the evidence, or they don't want a conservative litmus tests that is quite so judicially efficient, or as you say "useful".