An e-mailer says conservatives don’t do bumper stickers (and we have this thread every four years, don’t we?):

I’ve noticed this phenomenon since the ’80s. In my experience,
Republicans are much more hesitant to festoon their vehicles with a
candidate’s bumper stickers than are Democrats. Ditto with yard signs.
In fact, in 2004 you’d have predicted that Kerry would have taken my
district by 30 percentage points, judging by the disparity in bumper
stickers and yard signs. Bush, however, won comfortably. I think it
has to do with conservatism- we’re much less interested in making
spectacles of ourselves. We do, however, vote, and in larger numbers
than the Dems.