“In the early phase of the primaries, Parscale launched Trump’s digital operation by buying $2 million in Facebook ads—his entire budget at the time. He then uploaded all known Trump supporters into the Facebook advertising platform and, using a Facebook tool called Custom Audiences from Customer Lists, matched actual supporters with their virtual doppelgangers and then, using another Facebook tool, parsed them by race, ethnicity, gender, location, and other identities and affinities. From there he used Facebook’s Lookalike Audiences tool to find people with interests and qualities similar to those of his original cohort and developed ads based on those characteristics, which he tested using Facebook’s Brand Lift surveys. He was just getting started. Eventually, Parscale’s shop was reportedly spending $70 million a month on digital advertising, most of it on Facebook. (Facebook and other online venues also netted Trump at least $250 million in donations.)

While it may not have created individual messages for every voter, the Trump campaign used Facebook’s vast reach, relatively low cost, and rapid turnaround to test tens of thousands and sometimes hundreds of thousands of different campaign ads. According to Issie Lapowsky of Wired, speaking with Gary Coby, director of advertising at the Republican National Committee and a member of Trump’s digital team:

On any given day…the campaign was running 40,000 to 50,000 variants of its ads, testing how they performed in different formats, with subtitles and without, and static versus video, among other small differences. On the day of the third presidential debate in October, the team ran 175,000 variations. Coby calls this approach “A/B testing on steroids.””

How He Used Facebook to Win
https://www.nybooks.com/articles/2017/06/08/how-trump-used-facebook-to-win/
via Instapaper