As of February 2008, white law requires an Obama 08 bumper sticker to be placed on the back of every Prius. Though these stickers reach peak effectiveness during an election year, it is acceptable to leave this sticker on the car until the next election regardless of whether or not the candidate actually won. If it’s a disputed election like in 2000, the sticker can be left on for the life of the car.
If a white person does not feel like supporting a candidate, they will likely select a bumper sticker that tells other people what to do. Some popular ones include telling people to Coexist and to stop eating meat.
http://stuffwhitepeoplelike.com/2008/05/21/100-bumper-stickers/