The techniques are only a couple of thousand years old, or more:
"But the chief priests and the elders persuaded the crowds to ask for Barabbas and to put Jesus to death."
In the market place, a voice over your shoulder. You turn, but the speaker has moved on, to repeat his message.
You can do it to smash an individual, as Google allegedly did to James Damore; or public figures like Farage, Trump etc; or issues like Brexit.
There they are, the voices in but not of the crowd, supplying the insults, insinuations, cartoons, factoids, distraction issues for "Facebook simple"... and the coaches and placards, the knots of "representative" people on St Stephen's Green, the agents provocateurs...
On Saturday my wife and I were shopping, and on the pavement was a stand with two people asking passers-by to write on a Post-It and stick it on a board to "have our say" as to "What Should We Do About Brexit?"
I said to the nice lady, "Leave, obviously" and the shutters came down behind her eyes and her mouth repeated my words in puzzlement. If I'd bothered to write a notelet for this primary-school exercise, would it have stayed long on the board?
But if you sow division and confusion, that is half the battle.
Democracy can be managed.