In the age of Facebook, it has become far easier for campaigners or marketers to combine our online personas with our offline selves, a process that was once controversial but is now so commonplace that there’s a term for it, “onboarding.” Cambridge Analytica says it has as many as 3,000 to 5,000 data points on each of us, be it voting histories or full-spectrum demographics — age, income, debt, hobbies, criminal histories, purchase histories, religious leanings, health concerns, gun ownership, car ownership, homeownership — from consumer-data giants.

No data point is very informative on its own, but profiling voters, says Cambridge Analytica, is like baking a cake. “It’s the sum of the ingredients,” its chief executive officer, Alexander Nix, told NBC News. Because the United States lacks European-style restrictions on second- or thirdhand use of our data, and because our freedom-of-information laws give data brokers broad access to the intimate records kept by local and state governments, our lives are open books even without social media or personality quizzes.

Ever since the advertising executive Lester Wunderman coined the term “direct marketing” in 1961, the ability to target specific consumers with ads — rather than blanketing the airwaves with mass appeals and hoping the right people will hear them — has been the marketer’s holy grail. What’s new is the efficiency with which individually tailored digital ads can be tested and matched to our personalities. Facebook is the microtargeter’s ultimate weapon.

The explosive growth of Facebook’s ad business has been overshadowed by its increasing role in how we get our news, real or fake. In July, the social network posted record earnings: quarterly sales were up 59 percent from the previous year, and profits almost tripled to $2.06 billion. While active users of Facebook — now 1.71 billion monthly active users — were up 15 percent, the real story was how much each individual user was worth. The company makes $3.82 a year from each global user, up from $2.76 a year ago, and an average of $14.34 per user in the United States, up from $9.30 a year ago. Much of this growth comes from the fact that advertisers not only have an enormous audience in Facebook but an audience they can slice into the tranches they hope to reach.

One recent advertising product on Facebook is the so-called “dark post”: A newsfeed message seen by no one aside from the users being targeted. With the help of Cambridge Analytica, Mr. Trump’s digital team used dark posts to serve different ads to different potential voters, aiming to push the exact right buttons for the exact right people at the exact right times.