These really couldn't be simpler, which, as a career advertising guy, is the sort of communication that I'm partial to. You've got the car-related aspects in the choice of left or right and in being the color of highway signs, and they mock Obama with precious little effort.
Bumper stickers, like billboards, pretty much have to stand on their own rather than be explained in any way, so I won't. If they move you, they move you. Reality. Hope. America. Prosperity.
Also, some anti-Obama bumper stickers I slapped together rather quickly, and some others that were designed to be placed on stop signs, if you're of a mischievous bent.