Matt Bai makes a really good point about trying to predict how a Republican governor will act in the White House:

We in the media have historically embraced the story of the Republican governor who, it turns out, isn’t as much of a crazy conservative as you might think. Hey, look, the Tin Man has a heart! George W. Bush was a “compassionate conservative” who worked amiably across the aisle with Democrats. Mitt Romney passed a landmark, bipartisan bill to provide healthcare. Even Ronald Reagan enacted a huge tax increase while governor of California. And so on.

There’s just one problem with this formulation, which is worth remembering if Huckabee pulls off a remarkable win on primary night in Iowa: it is a serious misreading of conservative doctrine and a lousy predictor of what’s to come.

Here’s why: ... Under the doctrine of federalism, the government in Washington is supposed to remain meek and disengaged in domestic affairs, leaving policy and funding decisions primarily to the states.... That’s the whole point of the conservative exercise—to make state government set priorities and scale back waste and unnecessary commitments. You’d be hard pressed to find a Republican governor ... who hasn’t had to raise some tax or fight for a worthy social program. That’s just what governors do—especially since almost all of them are bound by law to balance their budgets.

When these governors get to Washington, though, that’s a different story—and there’s nothing inconsistent about it. Then their job, as they see it, isn’t really to govern anymore, but to whack at the hopelessly gnarled federal bureaucracy and push the burden for domestic programs back to the states, where it belongs. So while Bush may have been a pleasant enough conciliator and dealmaker in Texas, he never for a minute confused the demands of that job with the one he had taken on at the White House. And neither, one can presume, would Mike Huckabee. He may have been a reasonably centrist governor, but he’d be a starkly conservative president.