I've seen a Volt with a PA plate with a "Powered by coal" sticker. Some people are supportive of coal.
If you want to clean up electricity, sell lots of electric cars, so you'll have massive economies of scale in battery manufacturing, lower the cost of batteries, help make batteries ubiquitous on the grid, and then you'll be able to integrate a lot more renewable power more easily.
Right now, I don't care if it's powered by coal or powered by sun, I want it with a battery and powered by electricity.