Not a campaign sign, but we have a sign on our front walkway that says “no solicitors, no loiterers, no trespassing”. Since the door-to-door people don’t understand what those big words mean (we still get solicitors), I’m going to replace it with one that tells door knockers that we will charge them for every minute we have to listen to their schpiel, payable in advance.
https://www.amazon.com/BOEYC-1-12x8-Inch-Shuo10/dp/B0881RGNCH
a neighbor down the way has a backhoe featured prominently in the front with a simple sign that reads “don’t make me use this”. never seen a solicitor of any kind at their house. even the jw’s don’t go to their house. might have to get one.