I mean this genuinely - how do we know that CA impacted the election? How many votes were swung or non-voters converted?

I go back and forth. Sometimes I think this stuff must be super valuable because so much money gets spent in it. Then I work with medium businesses who have no clue how effective their spend is.

I mean this sincerely: what actual evidence is there that CA affected the 2016 election?

1. Advertisers wouldn't spend so much money if it didn't work

2. ...?