Assumption: Prius drivers disproportionately lean to the left, just as Volvo drivers lean left – or at least used to. I don’t have statistics verifying that but it seems to be the case.
Why? I think it has just as much to do with the body style than it does with the gas mileage. The Prius body style to me looks nerdy. Likewise, Volvo body styles, with their boxy look, used to be nerdy (now they’re more mainstream). And for some reason, people who like the nerdy look tend to lean left.
As far as the high gas mileage aspect of the Prius, righties should be just a likely as lefties to be attracted to that. Granted, lefties more than righties likely would be attracted to hybrid cars because they think* they’re helping the environment. But righties would be more likely than lefties to be attracted to hybrid cars based on the reason that they think they’re saving money in the long run (assuming the purchase price isn’t overwhelmingly higher than a non-hybrid equivalent). Savers tend to be righties and spenders tend to be lefties, both when it comes to personal finances and national finances.
So in the end, the reason you saw more Obama bumper stickers than McCain bumper stickers on Priuses has got to be the nerdy body style.
* “Think” is the operative word. They may think they’re helping the environment, but they’re harming it. Anytime you drive around a half-ton machine that requires the laying of thousands of square miles of pavement and associated destruction of trees and natural habitat, that requires the construction of habitat-destroying and energy-consuming automotive factories, that requires the extraction and distribution of oil and other natural resources, that emits pollutants into the air, that generates a bit of noise pollution, and that to some observers generates sight pollution (i.e., the nerdy look), you’re not helping the environment at all. While you may be harming it a little less than, say, an SUV, it’s microscopically less. And you’re destroying the environment much more than the ever-hated (by lefties) snowmobiles and four-wheelers, which don’t require the paving over of natural habitat.
If you really want to help the environment, then don’t buy a Prius. Or any car.