I'd add that for #2 they don't need to persuade people to change their vote with the adverts, or even mislead them (although the latter may help).

All they need to do is target adverts reminding you to vote to the people who will vote the way they want.

Facebook ran an experiment in 2010 that shows they can definitely increase the chance of individual users voting: https://www.smithsonianmag.com/science-nature/how-a-facebook...