This article about how the campaign used targeted marketing and social media was posted previously, but is worth repeating (and the link has changed).
It was called "Trump Knows You" but is now titled "The Data That Turned the World Upside Down": motherboard.vice.com/en_us/article/big-data-cambridge-analytica-brexit-trump
It's all worth reading, but here's an excerpt relevant to the discussion about getting the vote out, and also about African-American voters.
"In the Miami district of Little Haiti, for instance, Trump's campaign provided inhabitants with news about the failure of the Clinton Foundation following the earthquake in Haiti, in order to keep them from voting for Hillary Clinton. This was one of the goals: to keep potential Clinton voters (which include wavering left-wingers, African-Americans, and young women) away from the ballot box, to "suppress" their vote, as one senior campaign official told Bloomberg in the weeks before the election. These "dark posts"—sponsored news-feed-style ads in Facebook timelines that can only be seen by users with specific profiles—included videos aimed at African-Americans in which Hillary Clinton refers to black men as predators, for example."