For perspective, compare the number of people who aren't wearing buttons and the number of cars that don't have any bumper stickers on them at all to the number with political stickers.
What you'll find is that only the hard-core sport the stickers and buttons. Your survey reflects the number of die-hards. It's the die-hards who wear the buttons and put the stickers on their cars...a very small percentage of the voting population.
The phrase "silent majority" comes to mind, in fact.
5 Legislative Days Left Until The AWB Expires