The headlines were about Facebook admitting it had sold ad space to Russian groups trying to sway the 2016 presidential campaign. But investigators shrugged: they’d known or assumed for months that Facebook, as well as Twitter and other social-media platforms, were a tool used in the Kremlin’s campaign. “The only thing that’s surprising is that more revelations like this haven’t come out sooner,” said Congressman Mike Quigley, an Illinois Democrat and a member of the House Intelligence Committee. “And I expect that more will.”

Mapping the full Russian propaganda effort is important. Yet investigators in the House, Senate, and special counsel Robert Mueller’s office are equally focused on a more explosive question: did any Americans help target the memes and fake news to crucial swing districts and wavering voter demographics? “By Americans, you mean, like, the Trump campaign?” a source close to one of the investigations said with a dark laugh. Indeed: probers are intrigued by the role of Jared Kushner, the now-president’s son-in-law, who eagerly took credit for crafting the Trump campaign’s online efforts in a rare interview right after the 2016 election. “I called somebody who works for one of the technology companies that I work with, and I had them give me a tutorial on how to use Facebook micro-targeting,” Kushner told Steven Bertoni of Forbes. “We brought in Cambridge Analytica. I called some of my friends from Silicon Valley who were some of the best digital marketers in the world. And I asked them how to scale this stuff . . . We basically had to build a $400 million operation with 1,500 people operating in 50 states, in five months to then be taken apart. We started really from scratch.”

Kushner’s chat with Forbes has provided a veritable bakery’s worth of investigatory bread crumbs to follow. Brad Parscale, who Kushner hired to run the campaign’s San Antonio-based Internet operation, has agreed to be interviewed by the House Intelligence Committee.

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Bigger questions, however, revolve around Cambridge Analytica. It is unclear how Kushner first became aware of the data-mining firm, but one of its major investors is billionaire Trump backer Robert Mercer. Mercer was also a principal patron of Breitbart News and Steve Bannon, who was a vice president of Cambridge Analytica until he joined the Trump campaign. “I think the Russians had help,” said Congresswoman Jackie Speier, a California Democrat who is a member of the House Intelligence Committee. “I’ve always wondered if Cambridge Analytica was part of that.” (Cambridge Analytica did not respond to a request for comment.)

Senator Martin Heinrich is leading the charge to update American election laws so that the origins of political ads on social media are at least as transparent as those on TV and in print. Heinrich, a New Mexico Democrat, is also part of the Senate Intelligence Committee that is tracing Russia’s 2016 tactics. “Paul Manafort made an awful lot of money coming up with a game plan for how Russian interests could be pushed in Western countries and Western elections,” Heinrich said, referring to a mid-2000s proposal Manafort pitched to a Russian oligarch. “Suddenly he finds himself in the middle of this campaign. If there is a person who I think is very sophisticated in this stuff, and runs in pretty dicey circles, that is the place where I would dig.”