Conservatives take it as a given that the mainstream press has been hostile toward Donald Trump since he declared his candidacy for president. And it’s true that there’s been no small amount of critical reporting since his inauguration. But a new study of the online “media ecosystem” by researchers at Harvard’s Berkman Klein Center for Internet and Society finds that throughout the 2016 campaign the political press consistently focused its coverage of Trump on the key issues he was running on—immigration, jobs, and trade—and just as consistently focused on Hillary Clinton’s scandals to the exclusion of the issues she ran on. Overall, the tone of the coverage of both candidates was negative, but the difference in the content clearly worked to Trump’s advantage, perhaps decisively so.

According to the study’s lead researcher, Harvard legal scholar Yochai Benkler, this wasn’t only a matter of lazy he-said/she-said journalism. And it wasn’t, as some have speculated, just a result of the widespread assumption during the campaign that Clinton would win. There’s an element of truth in both of those explanations, but Benkler says that, in instances, this imbalance was the result of the mainstream media’s “being played, or manipulated, by a very sophisticated and disciplined right-wing messaging campaign.”

The numbers are stark. Looking only at mainstream sources—like The New York Times, Politico or CNN—the researchers identified almost 70,000 sentences about Clinton’s e-mails, which dwarfed the number of references to all other topics for both candidates. After that, there were around 22,000 mentions of the Clinton Foundation. The issue associated with Clinton that got the most attention was jobs, which were mentioned in around 15,000 sentences. Overall, sentences mentioning Clinton’s various scandals outpaced those focused on her agenda by a ratio of around four to one. (This finding is consistent with another study released by Harvard’s Shorenstein Center for Media Politics and Public Policy last December.)

The opposite was true in coverage of Trump. Whether it was his refusal to release his tax returns, allegations of sexual harassment and assault by over a dozen women, his fraudulent university, or his foundation’s raising money for dubious purposes—none of these stories was mentioned more than 10,000 times. Jobs, immigration, and trade, on the other hand, were mentioned in stories about Trump over 75,000 times.

The study relied on a set of analytic tools called Mediacloud that the Harvard team and their colleagues at MIT developed over the past nine years. Their system analyzes who reads news stories, which outlets cite them, and who shares them across social media. It places news outlets on the ideological spectrum by looking at cross-linking patterns between sources, the reach of stories on Twitter and Facebook and the ratio of tweets by partisan influencers on the left and the right. To complement this “big data” approach, researchers also took a more granular look at certain stories, developing brief case studies of how they developed, how widely they were disseminated and by whom. Their database contains information about the content and spread over two million articles published during the 18 months leading up to Election Day.

A couple of different dynamics contributed to the disparity in mainstream coverage. The authors write that “an unusual pattern of support for Trump” in 2016, “some right-leaning outlets, most notably Breitbart, launched attacks targeted not only at Democrats and Trump’s Republican rivals but also at media outlets that did not fully support Trump’s candidacy.” Many of these intra-partisan disputes centered on immigration and trade. On the latter, Trump broke with what had long been the orthodox Republican view that trade was a net benefit for the economy. On immigration, “Breitbart rose to serve as a focal point for Trump supporters and media organizations on the far right…serv[ing] as a translator and bridge that helped to legitimate extreme views on topics such as immigration and anti-Islamic sentiments.” Mainstream reporters are always attracted to intra-party fights, and mainstream conservatives opposed to Trump were more likely to focus on his outrageous claims about Islam and violent immigrants than on Trump University’s ripping off its students.

Among partisan Democratic outlets, there was significantly less conflict over the issues. By the end of the bruising primaries, Hillary Clinton’s agenda was similar to that of Bernie Sanders’s, but debates about her trustworthiness and integrity continued. On both the left and the right, the Clinton scandals dominated her coverage, so it only follows that this in turn informed the mainstream reporting.

Another key finding was that “the structure and composition of media on the right and left are quite different,” in large part because “the leading media on the right and left are rooted in different traditions and journalistic practices.” And these differences, the researchers argue, played an important role in the campaign.

Media polarization has gotten a lot of attention in recent years. But Yochai Benkler says that his team found that media polarization in 2016 was asymmetrical. “It’s not the same on the left and the right. Essentially, everyone from the center right—from publications like National Review or The Wall Street Journal—all the way to the left, at publications like Mother Jones, had a more or less normal distribution, in the sense that most of the attention was given to [reporting in] the older, more professional media like The New York Times, The Washington Post, and CNN. Whereas what happened on the right is that the more you were shared and used by [conservatives], the more attention you got.” The conservative media were largely walled off from the rest of the ecosystem, linking to and sharing content from like-minded sources. As a result, a handful of outlets—led by Breitbart, which played a dominant role on the right—formed a sort of nucleus of online media on the right. The broad left was as likely to share a story from The Hill as they were a piece from The Nation, while the right—other than the “never Trump” types at some center-right outlets—tended to stay inside the bubble.

“People on both sides did go to the other side to try to find evidence to support their own position,” says Benkler. “And the big difference was that the right-wing media was very message disciplined, so there was very little for people outside of the right-wing to find there, whereas the more traditional journalistic media [and the left] had negative coverage of both candidates.”

That asymmetry left both sides vulnerable to different kinds of manipulation, according to the authors. “The more insulated right-wing media ecosystem was susceptible to sustained network propaganda and disinformation, particularly misleading negative claims about Hillary Clinton,” they wrote. “Claims aimed for ‘internal’ consumption within the right-wing media ecosystem were more extreme, less internally coherent, and appealed more to the ‘paranoid style’ of American politics than claims intended to affect mainstream media reporting.” Think about the feverish stories told by Alex Jones, The Gateway Pundit, or Mike Cernovich.

Meanwhile, traditional journalism, with its standards of balance and goal of objectivity, continued to get the most attention on the center-left and the left, and the authors note that these very “journalistic practices were successfully manipulated by media and activists on the right to inject anti-Clinton narratives into the mainstream media narrative.” This is how, despite being walled off from the rest of the media landscape, stories that originated in the right’s echo chamber were nonetheless able to make the leap into the mainstream.

This was evident in coverage of the Clinton Foundation. While there was some legitimate criticism of how its funds were spent, the allegations of corruption never amounted to more than innuendo. It nonetheless was mentioned in more sentences in the mainstream press than any of Trump’s more substantial scandals or Clinton’s policy positions.

Allegations that the Clinton Foundation tied the Democratic candidate to radical Islamists and Russia began in the fever swamps of the right, but when Clinton Cash author Peter Schweizer, then a “senior editor at large” at Breitbart, gave The New York Times an exclusive in advance of the book’s publication, those allegations got mainstream footing. “it provided a key narrative within the right-wing media ecosystem to establish belief in both the personal corruption of Hillary Clinton and the ‘fact’ that she had sold out U.S. policy interests to historical and current strategic adversaries,” according to the study’s authors. Validated by the Times, the story was then picked up by the rest of the traditional media.

That was in the spring of 2015, and despite a rash of reports immediately following the Times story, it then remained largely confined to the conservative media until the summer of 2016, when Hillary Clinton got a significant bump in the polls following the Democratic National Convention. At that point, the 18-month-old story, which had been validated by mainstream reports the year before, became a central feature of the campaign.

According to the study, this was a result of excellent media activism on the right. Just before the convention, Breitbart launched a movie based on Clinton Cash that “was edited to appeal to supporters of Bernie Sanders.” In announcing the release, “Breitbart quoted MSNBC and the Guardian as sources asserting that the movie was ‘devastating’ or ‘designed to stir up trouble’ at the convention.” Breitbart promoted the film by noting that “The New York Times, The Washington Post, ABC News, and other Establishment Media have verified and confirmed the book’s explosive revelations that Hillary Clinton auctioned State Department policies to foreign Clinton Foundation donors and benefactors who then paid Bill Clinton tens of millions of dollars in speaking fees.”

At that point, the wall of separation between the right and the rest of the media universe collapsed, and “instead the Daily Caller, Breitbart, and Fox [were] all clustered around the New York Times and [were] linking to its 2015 coverage as a source of validation for their…stories.”

That case study doesn’t negate other media analyses, but it highlights that in an increasingly complex ecosystem where traditional reporting, opinion, and hyperpartisan clickbait vie for attention in fractured social-media circles, a concerted effort to shape the conversation by savvy activists like Stephen Bannon can pay big dividends for a campaign.

“This was a stark finding,” says Benkler, “as here we had the right-wing media being relatively insular, but still able to shape the agenda in such a way that the traditional media, which had many more viewers overall, followed the same narrative consistent with both the Trump campaign and the right-wing media.”

Studies consistently show large partisan and ideological divides when it comes to faith in the mainstream media. On the left, criticism of sloppy or biased reporting and false equivalencies is common, but there remains a certain degree of faith in the underlying process of “neutral” journalism. This, according to the Harvard study, is a vulnerability. And conservative activists, who have long been told that the mainstream press isn’t just flawed, but actively hostile to their beliefs, appear to have learned how to exploit it.