On Tuesday, when news broke that Donald Trump’s former campaign manager Paul Manafort had shared internal polling data with Konstantin Kilimnik, a Russian business associate with ties to Russian intelligence, the through line between the campaign and the Kremlin began to look incontrovertible. The revelation came in an inadvertently unredacted court document, which was filed by Manafort’s lawyers in response to charges made by the special counsel, Robert Mueller, that Manafort had lied to investigators. According to the Times, some—but not all—of the data was already in the public domain. The rest came from the campaign’s own polling operation.

Trump, who famously eschewed polling in the early days of his campaign and told the “Meet the Press” host Chuck Todd that pollsters were a waste of his money, eventually had five polling firms working to get him elected. All were hired after Manafort joined the campaign, in March, 2016, without pay. Five months later, he was forced to resign when it was revealed that he had failed to disclose his work as a foreign agent on behalf of pro-Russia political forces in Ukraine. Since then, of course, Manafort has been convicted of multiple counts of financial fraud.

In June, Trump downplayed Manafort’s tenure on his campaign, telling reporters, “You know, Paul Manafort worked for me for a very short period of time.” But F.B.I. wiretaps show that Manafort continued his association with Trump long after he resigned. Manafort was also in touch with his business partner, Rick Gates—now considered to be Robert Mueller’s star witness—who had been Trump’s deputy campaign manager and remained a White House insider. But, even more significant, it was Paul Manafort who decided to hire Tony Fabrizio as the campaign’s chief pollster. Their friendship dates back to the nineteen-nineties—Fabrizio and Manafort worked together on the Presidential campaign of Bob Dole. Fabrizio also worked for Manafort in Ukraine, earning $278,500 for the same type of work he would later do for Trump—polling and surveying to help elevate Viktor Yanukovych’s Party of Regions in the 2012 parliamentary elections. During the same period, Manafort disbursed five hundred and thirty-one thousand dollars to Kilimnik, his translator and fixer in Ukraine, for “professional services.” According to a report in Bloomberg about Manafort’s Ukrainian ventures, Fabrizio is included in e-mail chains with Manafort and Kilimnik.

Fabrizio, a native New Yorker who now lives in Florida, has worked for dozens of Republican candidates, including Mitch McConnell, Joni Ernst, and Rand Paul, and is a senior counsellor at Mercury Public Affairs, which Mueller referred to federal prosecutors in the Southern District of New York, for failing to register as a foreign agent for its lobbying work on behalf of Ukraine. Fabrizio’s company, Fabrizio, Lee & Associates, bills itself as “one of the leading survey research and campaign strategists in the nation.” “We were honored to have the privilege to serve as Chief Pollsters for President Donald J. Trump’s historic upset victory,” the company’s Web site declares, at the top of its home page. But the firm also had the experience of many people who have worked for Trump: for a time, it was reported that Trump stiffed the company three-quarters of a million dollars for its services on the Presidential campaign. If nothing else, Fabrizio was familiar with both principals in this story. (Fabrizio did not respond to multiple requests for comment.)

Adam Geller, the founder and C.E.O. of National Research, a Republican polling firm that worked with Fabrizio on the Trump campaign, told me, “I honestly have no idea what was and wasn’t shared with the Russians.” In the final months of the race, National Research was responsible for polling in Michigan, Wisconsin, Missouri, and Iowa. By then, Manafort, whom Geller never had any direct contact with, had left the campaign. (Another polling firm employed by Trump was the Polling Company, whose C.E.O., Kellyanne Conway, replaced Manafort as campaign manager after he resigned.) But, for a time, Fabrizio was at the helm of Trump’s polling operation, and it was his job to share polling information with Trump’s campaign manager. The contested swing states that Trump narrowly—and surprisingly—won, such as Michigan and Wisconsin, were also places where both the Trump campaign and Russia’s Internet Research Agency focussed their efforts. Herein lies at least one answer to the question of why Russia would want the Trump campaign’s polling data: it potentially offered demographic targets for Russia’s bots and propaganda.

In her analysis of five million paid, issue-based Facebook ads—which covered such hot-button issues as gun rights, abortion, gay rights, immigration, terrorism, and race—during a six-week period of the 2016 Presidential campaign, the University of Wisconsin professor Young Mie Kim discovered that “the most highly targeted states—especially Pennsylvania and Wisconsin—generally overlap with the battleground states with razor thin margins.” These were ads placed by two hundred and twenty-eight groups, many of which were later linked to the Internet Research Agency. Kim also found that these efforts were calibrated to appeal to certain demographics. Low-income white voters, for example, were targeted with ads focussing on immigration and race.

An even more comprehensive analysis, by Oxford’s Computational Propaganda Project, which was released last month, shows just how pervasive Russia’s inflammatory targeting was. “On Facebook, the five most shared and the five most liked posts focused on divisive issues, with pro-gun ownership content, anti-immigration content pitting immigrants against veterans, content decrying police violence against African Americans, and content that was anti-Muslim, anti-refugee, anti-Obama, and pro-Trump,” the researchers wrote. The posts developed by the Internet Research Agency “tended to mimic conservative views against gun control and for increased regulation of immigrants. In some cases, terms such as ‘parasites’ were used to reference immigrants and others expressed some tolerance of extremist views.” These posts increased almost seven-fold between 2015—before Manafort joined Trump’s team—and 2016, when he, and the pollsters he hired, were guiding the campaign.

Not long after the election, in an interview with “Frontline,” Fabrizio offered a glimpse of how this data was gathered and how crucial it was to Trump’s victory. “One of the groups that we created early on in the campaign from the polling was what I called Trump targets,” Fabrizio said. “These were voters who wanted to change direction, wanted a new direction, weren’t voting for Trump, weren’t hardcore Democrats, weren’t hardcore liberals, weren’t hardcore Hillary supporters.” Knowing whom to target, where they were, and which issues resonated with them gave Trump’s digital team crucial information for its advertisements and social-media messaging. “We would report out to the senior team what markets those voters were concentrated in,” Fabrizio told “Frontline.” “In Florida, literally, if you changed four counties in Florida, twenty-nine electoral votes would have been off the table. Four counties.”

When Kost Bondarenko, one of Manafort’s longtime Ukrainian associates, told the Daily Beast, in May, 2017, that “Trump won because of Manafort,” this is what he may have meant.

Fabrizio’s polling also showed something else: from the start, Trump’s overt racism—his claims that Mexicans were rapists and Muslims were terrorists, for example—was popular. “When he’d say things that people were, like, ‘Oh, this is it, this is going to be the thing that breaks him,’ ” Fabrizio said, “it actually just reinforced in the minds of Republican primary voters . . . that, if he had the guts to say what other people wouldn’t say, then, you know what? He’d shoot straight with them. And that’s what they were looking for.” The Internet Research Agency, we now know, also exploited Americans’ xenophobia and prejudices, tendencies that had been lurking close to the surface of U.S. politics long before Trump came along. But knowing where to direct their Facebook ads and Instagram posts would have been quite useful. (It should be noted that Russia engaged in a similar socially divisive online campaign on behalf of Manafort’s client, Viktor Yanukovych, in Ukraine.)

Once Russian efforts to destabilize the American electorate and promote Donald Trump’s candidacy were revealed, there appeared to be a strange and inexplicable synergy between the Trump campaign and Russia’s propaganda offensive. When Senator Mark Warner, a Democrat of Virginia and the ranking member of the Senate Intelligence Committee, spoke on the podcast “Pod Save America,” in April, 2017, he wondered if the Trump team’s data had been passed along to the Russians, given their uncanny ability “to target states and levels of voters that the Democrats weren’t even aware” of. At the time, all eyes were on Brad Parscale, Jared Kushner, and their digital team, especially Cambridge Analytica, whose swing-state targeting was suspiciously spot-on. But it seemed to be one of the few instances in which Manafort, who had left the campaign shortly after Cambridge Analytica had been hired, escaped public scrutiny. Mueller, who had launched his investigation a month earlier, has long had his sights on Manafort. We now know that his investigation into the former Trump-campaign chairman involves far more than financial crimes.