Give it a few years and they'll be running "plata o plomo"[1] ads targeting specific policy makers. On one side there will be an image of a suitcase full of money, and the other an image of a policy maker's child with a target on their head.

[1] "Plata o plomo" means "silver or lead" in Spanish. Pablo Escobar would bribe government officials and law enforcement by telling them that they could choose silver (money) or lead (a bullet).

Facebook won't need to resort to such crude methods. They can algorithmically suppress positive stories about a candidate, boost negative stories, and do the opposite for his opponent.

Without a leak from Facebook, you wouldn't even know they did anything at all, let alone be able to prove it.

Story choice in traditional news media has a similar bias.