Obama Bumper Stickers on cars on US 101 in Silicon Valley since about 2010. From 2007 to 2010, until one month after the election, that is all you saw. Then people figured out how to scrape them off. You can still see the mars on the paint on most cars.
See very few (the total exception) of the new 2012 Obama campaign stuff or stickers. Guess some people don't want to advertize now.......?
Disclaimer, yes, the occasional really creepy car with every progressive left cause and Obama. Ocassionally.