Also from John McCain's press conference this morning, the senator from Arizona once again makes it clear that he doesn't really understand cap-and-trade:

QUESTION: The European Union has set mandatory targets on renewable energy. Is that something you would consider in a McCain administration? [...]

MCCAIN: Sure. I believe in the cap-and-trade system, as you know. I would not at this time make those -- impose a mandatory cap at this time. But I do believe that we have to establish targets for reductions of greenhouse gas emissions over time, and I think those can be met.

Which is, of course, completely out of line with his own proposal for a cap-and-trade scheme, both the plan he proposed with Joe Lieberman last year and his own presidential plan, released last month. They both would, by nature, be mandatory -- hence the "cap" in the name. This isn't the first time McCain has misunderstood his own policy on cap-and-trade. In the Republican debate in Florida in January, he also denied that his cap-and-trade program included a mandatory cap on carbon.

He also appeared confused about the definition of cap-and-trade in an interview with Greenwire ($ub req'd):

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.