Republican presidential candidate John McCain has called for a change in federal policy that would allow coastal states to choose whether to allow oil exploration in offshore waters.

The proposal did not go down well with most U.S. environmentalists. The reaction of groups in lockstep with Democrats, such as the Sierra Club, was scathing.

But there was more in McCain’s Houston speech than offshore drilling.

McCain reiterated his position that the U.S. must adopt a cap-and-trade plan to cut greenhouse gas emissions. Anyone who thinks that’s an easy sell in Texas should have been to the state Republican convention in Houston last weekend. There, you would have heard earnest people insisting that sunspots are the cause of global warming.

McCain said that conservation is more than a personal virtue. That was a clear rebuke of Vice President Dick Cheney, who in 2001 said that conservation may be virtuous but cannot be the sound basis of an energy policy. Yes it can, Mr. Vice President. It must. Conservation is the foundation for shifting towards what McCain called an energy economy of “new and cleaner power sources.”

Finally, McCain reiterated his opposition to oil drilling in the Arctic National Wildlife Refuge, a 19 million-acre Alaska nature reserve that was established by the Eisenhower administration in 1960. That’s not an easy sell in Texas either. In fact, it’s not an easy sell for Republicans in most states.

In U.S. energy politics, the Arctic Refuge is the Holy Grail for both conservationists who want to keep America’s largest wildlife sanctuary pristine and the pro-drilling crowd, which is moved to tears about the billions of barrels of oil thought to exist beneath the refuge’s coastal plain.

Support for drilling “AN-WAHR” is de rigueur in many Republican circles. It is common to hear drilling supporters, most of whom haven’t stepped within a thousand miles of the place, call the refuge a barren wasteland. For those of us who have been privileged to visit the distant refuge, its silent beauty is extraordinary. McCain’s reason for bucking party orthodoxy on this issue is spot-on. Drilling the Arctic refuge and other special places would be as awful as drilling the Grand Canyon or the Florida Everglades.

So why does McCain support more offshore drilling? Even if his plan were adopted now, there is no way it would add supplies anytime soon. Many U.S. states don’t want it. California, for example, is very particular about protecting sugary beaches that draw hordes of spendthrift tourists. And a worldwide shortage of the pricey rigs needed for deepwater drilling will hamper exploration for a few years yet.

There are a couple of reasons for the stance he has taken. One is that McCain thought it important to send a signal to OPEC that the U.S. has other plans for meeting its energy needs besides begging the cartel’s potentates to loosen the knobs a bit.

Another is the peculiar Electoral College system by which America elects its presidents. Both McCain and Barack Obama must appeal to diverse constituencies in order to secure the 270 Electoral College votes necessary for election.

That’s why Obama had kind things to say about coal when he visited the coal-mining states of West Virginia and Kentucky last month, even as his coal-hating environmental allies gnashed their teeth.

McCain is paddling a middle course on the environment that contrasts with both Obama on the left and current Republican dogma on the right. It’s a delicate exercise for McCain, who is trying to both build the diverse constituency he needs to win and to help his fellow Republicans rediscover their heritage as the party of Theodore Roosevelt.