It's not quote mandatory caps. It's cap-and-trade, OK. It's not mandatory caps to start with. It's cap-and-trade. That's very different. OK, because that's a gradual reduction in greenhouse-gas emissions. So please portray it as cap-and-trade. That's the way I call it.

Here's what Holtz-Eakin said:

... McCain's Greenwire response sounded confusing because he thought the interviewer was implying that there were mandatory caps on emissions for individuals and companies -- not on the system as a whole.

Still no explanation from the campaign for McCain's remarks in January's GOP debate in Florida. Here's that exchange:

Tim Russert: Senator McCain, you are in favor of mandatory caps.

McCain: No, I'm in favor of cap-and-trade. And Joe Lieberman and I, one of my favorite Democrats and I, have proposed that -- and we did the same thing with acid rain.

And all we are saying is, "Look, if you can reduce your greenhouse gas emissions, you earn a credit. If somebody else is going to increase theirs, you can sell it to them." And, meanwhile, we have a gradual reduction in greenhouse gas emissions.

To be fair, these examples don't establish that McCain flatly doesn't understand there's a mandatory cap in his cap-and-trade plan. A more likely explanation is that this is domestic policy and McCain simply doesn't have his heart in it. He strikes the right pose, but it's an inch deep -- he's not committed enough to it to overcome his instinctive conservative aversion to the word "mandatory."

He supports a "market-based program" to "beat climate change" in the abstract, but he also wants gas tax holidays, domestic drilling incentives, megapork for nuclear and coal, no boosts in sector-specific efficiency or fuel economy standards, limited public investment, and enormous tax cuts. When the abstraction bumps into the conservative interest group, the abstraction gives way.