We had the same thing going on here, only it was with mailboxes. My neighbors, myself and several others had Bush/Cheney signs in our yards. As soon as we put the signs up some local punk(s) would play mailbox baseball
every night. This only happened to the people who had Republican signs in their yards. My next door neighbor,
an elderly lady in her 70's put bricks in her mailbox one night. The next time the thug came around he got a broken arm for his trouble.
Broken cars, broken arms...ya know, sometimes election years can be fun :-)