If we end up with an Obama v. Romney/Giuliani/Thompson race, the green dynamic will be simple. The guy who wants to do something about global warming vs. the guy who prefers the energy status quo.
But if, as I’m now (wildly and irresponsibly) predicting, it’s an Obama v. McCain race, the dynamic shifts in some interesting ways.
If you’re a pessimistic sort, you might guess that McCain’s early and courageous advocacy on climate change will neutralize the climate issue. Something like this happened in 2000 — Bush promised to regulate CO2 as a pollutant, and in the media’s eyes that basically made the climate issue a wash. (Not that it actually was, of course, but nobody was paying close attention to the issue back then, least of all the media.) It got no traction or attention. Perhaps the same thing will happen in 2008; the issue will just fade into the background.
There’s another way of looking at it, though.
Think about national security. At least in the last few decades, it’s been viewed as an issue Republicans own. When elections turn on it, Dems lose. Dems try and try to be "tough," since that’s how competence on national security has been defined, but voters sensibly decide that in a choice between mild fakers trying to act tough and genuine tough guys, you go with the real tough guys. If that’s your issue, what you care about, why not choose the real thing?
In a similar way, green is an issue Dems still own. If attention and focus can be put on the climate issue, voters might have a similar calculus: Do I want the tax-averse, government-averse, war-hungry guy with a middling climate plan, or do I want the guy that’s going to go big on climate? If the election turns on green, voters might want the real deal, not the echo.
(The same sorts of considerations come into play on social issues like abortion, on which McCain is atypically liberal for an R.)
Anyway, should be interesting.