The data came from Facebook:
During Obama’s initial 2008 bid for office, his team had already embraced technology in a greater capacity than any before it, assembling massive email lists and other targeted initiatives that earned Obama historic fundraising tallies. But for 2012, campaign manager Jim Messina wanted to take things even further.
To get there, his staff needed to link what had previously been disjointed databases of voter information (collected by volunteers, pollsters, and other campaign workers) into a single, comprehensive pool unrivaled in detail and scope. Whereas most voter logs used by campaigns often list only names and telephone numbers, Obama’s advanced tool dove into specifics like age, race, district, and voting history: it allowed field workers to rank voters intelligently and not waste time chasing unlikely votes.