Big data give incumbents a big advantage, which seems to have surprised the Romney team. The Obama campaign has used cookies to track its supporters online since the 2008 election. It spent the past 18 months creating a new, unified database, factoring in some 80 pieces of information about each person, from age, race and sex to voting history. (The campaign denied reports that it tracked visits to pornography sites in its outreach algorithms.) The Romney campaign says it tried to match the Obama campaign’s collection and analysis of data but had to start from scratch and had just seven months after the primaries.

What does this mean for you? Voters need to develop buyer-beware habits. The era of politicianssaying the same thing to all voters is over. Campaigns aim to tell voters exactly what each wants to hear: data-driven pandering.

Another consequence is that efforts by the Federal Trade Commission and other agencies to regulate data mining in the name of privacy are destined to collapse. Last month, Sen. Jay Rockefeller (D., W.Va.) sent a letter to the top “information broker” companies, accusing them of being “elusive” about what data they collect. Companies such as Acxiom ACXM +2.30% and Experian replied that much of their information comes from government databases. They should also point out that political campaigns are among the most sophisticated users of the consumer data they collect.