WASHINGTON — In November 2016, Dipayan Ghosh was still reeling from Hillary Clinton’s defeat as he left what was supposed to be a celebration party at the Javits Convention Center in New York to attend morning meetings for his job at the Washington offices of Facebook.
As Mr. Ghosh, a former White House technology adviser to President Barack Obama, made the four-hour drive, troubling questions started nagging him. What if fake news on Facebook and other sites had an impact on voters? How did the campaigns and any outsiders use ads on the site to influence the election?
A few months later, Mr. Ghosh quit his job at Facebook, where he worked on privacy and public policy issues. On Tuesday, a Washington think tank, New America, and Harvard’s Shorenstein Center on Media, Politics and Public Policy published a report he co-wrote, asserting that technology behind digital advertising — the financial lifeblood of Facebook, Google and Twitter — has made disinformation campaigns more effective.
“The problems were much broader than we imagined, and it was not just about one tool or platform,” said Mr. Ghosh, who with his co-author, Ben Scott, worked on devising Mrs. Clinton’s tech policy platform. “It’s the profit model underlying the whole digital advertising system.”