They were getting a small number of users to fill out quizzes on Facebook. Unfortunately, the Facebook API gave them information not just about the user who filled out the quiz, but of all of that user's friends.
It was against the Facebook ToS, but the data was still provided easily via the API. That's what allowed them to quickly build a database of most eligible voters with very little direct outreach.
It was against the Facebook ToS, but the data was still provided easily via the API. That's what allowed them to quickly build a database of most eligible voters with very little direct outreach.