Introduction

Abstract The Democratic Party’s 2008 presidential nomination was supposed to be the inevitable coronation of Hillary Clinton. She was the most well-known candidate; had the most support from the party establishment, and had, by far, the most financial resources. Two big names (Al Gore and John Kerry) considered running, but decided they had no hope of defeating the Clinton machine. That left an unlikely assortment of lesser-knowns: a U.S. Representative from Ohio (Dennis Kucinich), the Governor of New Mexico (Bill Richardson), and several U.S. Senators: Joe Biden (Delaware), John Edwards (North Carolina), Chris Dodd (Connecticut), Mike Gravel (Alaska), and Barack Obama (Illinois). The nomination went off script. Obama was a first-term senator, a black man with an unhelpful name, but he excited voters. He raised enough money to be competitive in the Iowa caucuses and he persuaded Oprah Winfrey to campaign for him. Obama defeated Clinton by eight percentage points in Iowa and the race was on. Obama won the Democratic nomination and, then, the presidential election against Republican John McCain because the Obama campaign had a lot more going for it than Obama’s eloquence and charisma: Big Data. The Obama campaign tried to put every potential voter into its data base, along with hundreds of tidbits of personal information: age, gender, marital status, race, religion, address, occupation, income, car registrations, home value, donation history, magazine subscriptions, leisure activities, Facebook friends, and anything else they could find that seemed relevant. Some data were collected from public data bases, some from e-mail exchanges or campaign workers knocking on front doors. Some data were purchased from private data vendors. Layered on top were weekly telephone surveys of thousands of potential voters which not only gathered personal data, but also attempted to gauge each person’s likelihood of voting—and voting for Obama. These voter likelihoods were correlated statistically with personal characteristics and extrapolated to other potential voters based on their personal characteristics. The campaign’s computer software predicted how likely each person its data base was to vote and the probability that the vote would be for Obama. This data-driven model allowed the campaign to microtarget individuals through e-mails, snail mail, personal visits, and television ads asking for donations and votes.