"You can micro target political speech through non-digital channels such as mail, phones, doors, & addressable cable. Campaigns have been doing this for a LONG time - before the internet."
I think you are underestimating the level of micro targeting that FB and Google employ. If I'm trying to win Florida, theres districts that I know I can get, the gray areas, and the ones I know I will lose. If I go into those gray areas and systematically target small sub groups, to the level of only thousands or tens of thousands in each group, I can flip a whole state.
Theres a reason Google and FB are worth so much, its because all previous advertising is completely inferior to the level of targeting and information they have on their audiences.
'Visits msnbc.com' is no where near what you would need. More along the lines of:
Show married females from ages of 32 - 50 in <important county> my opinions on abortion.
Show single men ages 20 - 30 in <important county> my opinions on gun laws (if I'm pro gun).
etc...
Not only is this more accurate than older methods, its much cheaper. I can get instant feedback on which ads are working, iterate and tailor my message.