An old union trick is to wedge broken glass bottles forward of the rear tire and behind front tire, so no matter how one leaves a parking spot one of the tires runs over broken glass.
Whoops! Too bad you missed seeing that glass.
Roofing nails are also used.
So the glass doesn't necessarily mean it was "just an accident".
If the weather is anywhere near “good”; I walk to the polling place. If I must drive, I take the car WITHOUT stickers.
The Wife and I will wear purple shirts; thus we walk past the thugs unquestioned. {Her “red hat stuff” foils Acorn Radar}.