There are two types of billboard vandals. The (generally) young idiots who just vandalise any they come across. And there are those who target billboards of one party only, because they are partisans for another party.
The level of partisan damage seems to be unprecedented this election. Chester Borrows has facebooked that every single billboard of his in Wanganui City got destroyed overnight. I’ve heard similar stories in several other electorates. I suspect there is a degree of co-ordination occurring here. It’s one thing to opportunistically take a whack at a billboard as you pass it. But to destroy every billboard in a city is a major endeavour that would take a few hours.