The targeting can easily be neighbourhood, so you can say neighbourhood 1 (that likes Pizza) gets messaging that says candidate A loves pizza and everyone should get a free one, and also tells that neighbourhood that candidate B hates pizza. Then in another Neighbourhood that hates pizza they advertise the opposite.

You can get a reasonable approximation of that targeting in real life as well, but it is harder to hide that that is what you’re doing. Whereas with online targeting you are never aware that the other ads exist.