It's the cheapest and easiest way for a candidate with 40% approval (Trump) to win an election.
I get lots of imaginative, complex "doomsday" scenarios for the 2020, when the most destructive methods are simple.
Enough people learned from 2016.
My point is how cheap, easy, and effective this is compared to tampering with enough machines to make a difference, or stealing ballots from mailboxes.
(compared=operative word)
If you've supported Sanders, please expect to be hit with a blitz of messages intend to rile you and enrage you.
People operating these campaigns don't care about truth.
If you expect to get hit with campaign micro-targeting you, you are better able to withstand it.