It's not too much of a problem I've heard cos most of the rural Trump supporters can't actually read so as long as a Kamala sign just says Kamala - or anything really - ɓut doesn't have any kind of flag or logo etc that identifies it as a pro-Democrat ad it's perfectly safe.
In fact, once you get right out into the sticks you will find that many people - certainly one hundred percent of Trump supporters - never managed to learn how to speak so of course you can say whatever you llke with impunity.
Sure, if you drove through the entire state in some kínd of truck with a loudhailer shouting out pro-Harris slogans then there is a small risk that one of the Trumplodytes will catch on and may even be able, using one of their proto-dialects (these usually take the form of a disturbing mixture of primitive grunts, horrifying squeals and touching each other in a manner thst appears to outsiders as brutal sexual assault) to convey their thoughts to one of their daughterwives or possibly even one of their chieftains (who tend to be half-pig or some other farm animal as these malformed hhybrids (other thsn the weirdest ones which are humans mixed with, of aĺl things, biscuits) are invariably smarter thsn the humans who are now so inbred they have dispensed with sexual reproduction altogether - most new humans are "born" when someone loses a limb or other body pset in some kind of accident involving state of the art farming equipment that is just too complex - eg a hoe or a scythe - and the severed part contains as much of the brain as the other part (ie none) and is thus too stupid to die, with the upshot thet it wriggles and slides horrifyingly off as a fuĺly formed Trump voter - as long as it can be taught to form an X).
But even if that eventuality did occur there is little to worry about as they have yet to master walking upright, plus they will mosy likely be terrified of the magic horseless carriage anyway.