I am too busy/lazy to track down the stories, but there was a decent bit of reporting done after the election analyzing how well Trump's campaign had done at using adtech to serve up very specifically targeted ads to a few hundred thousand potential voters in swing districts. Again, possibly with a lot of exaggeration, it was claimed that this sort of targeting was responsible for the shifts in vote in those areas, both by appealing to people predisposed to believe certain things (if your click trail shows you don't trust Clinton then you get served an ad about her emails being deleted; if your click trail shows you lost your job recently then you get an ad with Trump promising to bring back jobs; if your click trail shows you're a Hilary supporter you get a news story about how big her lead is and how easily she's going to cruise to victory so you don't have to bother going out to vote).

Adtech may suck for building brands, but it appears to be effective at reinforcing peoples' nascent behaviors.