A Democrat in Michigan scrolled through a surge of nasty Facebook memes about Sen. Elizabeth Warren last week before fixing on one that captured his growing dislike of the candidate. It depicted her smiling face as a mask. Behind it was Hillary Clinton.

Matt Walters, 64, a retired factory worker and supporter of Sen. Bernie Sanders (I-Vt.), shared the image onward to eight Facebook groups and tens of thousands of potential eyeballs with a few taps on his smartphone — using a popular new mass-posting technique that allows ordinary Americans to operate with rapid-fire speed reminiscent of Russian bots and trolls in 2016.

In that small way, Walters contributed to a massive wave of hostile memes about Sanders’s Democratic rivals that both reflects the rising divisiveness in the party’s nominating contest and, in the view of social media experts, exacerbates it.

“I’d call it a force multiplier,” Walters, a onetime union activist, said of Facebook.

The volume and viciousness of the memes — portraying Warren (D-Mass.) as a snake, a backstabber and a liar — reflect how Facebook identifies and rewards emotionally charged content to generate reactions from its billions of users. That serves the company’s ad-driven business model, which equates engagement with profit. But it also, in the view of experts who study Facebook’s effect on political speech, distorts democratic debate by confirming biases, sharpening divisions and elevating the glib visual logic of memes over reasoned discussion.

Facebook’s “algorithm not only aggregates people, it activates people in a way that accentuates extremism,” said George Washington University professor Steven Livingston, director of the university’s Institute for Data, Democracy and Politics. “It inflames passions. It inflames the nature of the discourse.”

Facebook spokesman Andy Stone declined to comment for this story.

Since the beginning of 2019, nearly 3,000 active Facebook pages supporting Sanders have generated more than 290 million interactions — meaning shares, likes or other user actions — according to an analysis by Trevor Davis, a research professor at Livingston’s institute. For contrast, about 350 pages devoted to former vice president Joe Biden have generated just 9 million interactions; nearly 300 pro-Warren pages come in at under 20 million interactions.

That breakdown is vastly out of sync with projected support for the candidates in polls, which show Sanders gaining ground but still behind Biden in an average of surveys. This underscores a new reality: Facebook gives individual users power over public discourse disproportionate to their authority at the ballot box.

Such outsized influence once required significant resources — money for printed materials, access to a broadcast studio or time to reach people face-to-face. Now all it requires is a smartphone.

One popular technique introduced by Facebook last spring allows sharing to multiple groups with a few simple clicks on a mobile device, allowing enthusiasts such as Walters to broadcast their views even more quickly than before.

The rising popularity of the tactic among Sanders supporters may help explain the scores of images bashing Sanders’s opponents that have appeared in nearly simultaneous bursts in recent weeks, pushed out by highly networked clusters of Facebook users, according to Davis’s analysis. He did not find evidence that the campaign itself was involved in this activity, focusing instead on the informal Facebook activity by supporters.

No other Democrat’s supporters are engaged in behavior on a similar scale, which is more characteristic of the online movement galvanized by Trump. The president’s campaign aides have credited Facebook with his victory in 2016, when he poured money into advertising on the platform while also using organic posts on social media to speak directly to his followers, who responded with a torrent of posts backing him and lacerating his opponents.

Sanders has similarly embraced social media as a tool in the political revolution he promises, though the candidate’s posts hardly echo the personal insults lobbed by Trump. And the senator’s campaign distanced itself from the online attacks. “As the senator has said loudly and clearly, there is no room in the political revolution for abuse and harassment online,” said Sarah Ford, a campaign spokeswoman.

The pro-Sanders forums focus on a range of themes, including the senator’s independence from corporate interests and his opposition to President Trump. At the same time, many of the images that fill the groups and pages are strikingly negative about rival Democrats, depicting former South Bend, Ind., mayor Pete Buttigieg as a wine-swilling CIA plant with Republican leanings and Biden as a feckless politician who preys on women.

The meme shared by Walters, the retired Michigan factory worker, was just one of dozens of anti-Warren images circulating recently and one of several that portrayed her as the second coming of Clinton, whose own bid to become the first female president in 2016 ended in division and defeat for Democrats. The version that Walters reposted reached about 500,000 Facebook users on 50 groups since it began circulating on Facebook in September, according to Davis.

The Sanders and Warren campaigns are promising a detente after Warren accused Sanders of saying in a private meeting that a woman couldn’t win the White House, and Sanders denied having done so. But the memo hasn’t been received by denizens of the digital world. Sanders supporters who are active on Facebook described in interviews growing disenchantment with other candidates and rising concern that the system might be rigged against their candidate.

Already, the pro-Sanders crusade has spawned groups calling for protests at the party’s national convention in July should Sanders not emerge as the nominee. #BernieOrVest is their rallying cry, echoing the Yellow Vest demonstrations that have roiled France. In December, an activist wore one of the high-visibility vests for a picture with Sanders, which he proceeded to upload to a group, claiming falsely that the senator had endorsed their movement.

Walters said that before the recent controversy, Warren “would have gotten my vote if Bernie hadn’t won.” Now he’s not sure what he’ll do in November should another Democrat clinch the nomination. In 2016, he cast a ballot for the Green Party’s Jill Stein rather than vote for either Trump or Clinton, whom he had come to distrust and dislike.

As for the enthusiasm Sanders inspires on Facebook, Walters sees a political advantage — even if it tips into divisiveness.

“It worked for Trump,” Walters said.

Facebook’s move to groups

Though groups have been part of Facebook for many years, the company began emphasizing them in the aftermath of the 2016 election. That’s when Facebook founder and CEO Mark Zuckerberg heralded the online communities as a more intimate way for like-minded users to connect. He touted the feature not only as redress for the company’s missteps but, more broadly, also as a way to “turn around the whole decline in community membership we’ve seen for decades,” as he wrote in June 2017.

Changes in recent years have elevated the feature to the forefront of Facebook, including tweaks in 2018 that sought to emphasize content from groups in a user’s news feed over other material.

Amid these shifts, groups also have become forums for spam and hyperactive posting, as a cottage industry of tools emerged for more efficiently plastering the online spaces using scheduling and automation technologies. Advice proliferated online for posting rapidly while eluding the platform’s spam detectors, which enforce policies against excessive sharing in ways that confuse and anger users.

The hectic pace of memes spreading among Sanders supporters made some researchers suspect widespread use of automation tools and, possibly, a foreign-influence operation. Conspiratorial themes pushed in 2016 by Russian operatives, including claims about corruption in the Democratic Party, have reemerged with a fury.

But evidence this campaign season points most clearly to the frenetic work of aggrieved Americans who, distrustful of mainstream gatekeepers of information, turn to Facebook. There, the traditional guardrails of political discourse don’t exist, and individual users can share torrents of divisive memes and other charged content to audiences far beyond the “Friends” once central to the Facebook experience.

“Perhaps it’s not surprising that some of the tactics used by Russian actors against American voters in 2016 are now being used by American voters against each other,” said Philip N. Howard, head of Oxford University’s Computational Propaganda Project.

The pro-Sanders users appear deeply linked. The top 72 users engaged in simultaneous posting — broadly circulating the same content in a single second — have an average 41 direct connections to others in the same universe of groups, according to Davis’s analysis. Connections entail friendship or one user following another. Overall, he estimated that tens of millions of unique users like the pages in question or are members of the groups.

Some of the most active users operate multiple groups and pages, which can obscure the origin of a particular post. The page called “Woodland Spaces,” for example, features mainly nature photography and evocative poetry, but last week it accused Warren of a “smear campaign” against Sanders in a Facebook group called “Bernie’s Army of One Hundred Million Americans."

In other cases, untangling the web of common ownership reveals unseemly linkages. The same page, “Bernies Revolution Continues," that owns the “Bernie Sanders’ Rare Meme Repository” group also owns a group called “The Anti Corruption Movement,” which includes posts about “satanic Zionism," as well as positive memes about Trump.

‘Information is power’

One Sanders supporter who saw and reposted the anti-Warren meme shared by Walters was freelance journalist Cara Rogoff Greenberg, 69, who lives in New York City. With a series of taps on her smartphone, she regularly posted to “Jews for Bernie 2020,” “Bernie Sanders Bernstorming Network,” “#BernieOrVest” and 10 others.

Days after posting the meme showing Warren as a mask for Clinton, Greenberg said she was placed in “Facebook jail” — the popular colloquial term to describe restrictions imposed by the company, often for posting too frequently — but remains uncertain about what policy she violated and how. She posted a cartoon of a woman behind bars in the “Women for Bernie 2020” group.

“At first I thought it was because I was abusing the privilege, sharing to a dozen or more groups at a time, but others have commented on my own timeline (I am still able to post there) that this is happening with contributors to other public Bernie groups,” Greenberg wrote, generating 75 comments and 41 likes or other reactions. “Is it a technical block intended to prevent spam, or political repression, or FB’s concern about uncredited or false info being spread? I am concerned, and have been unable to easily figure out what is really going on here or how long this is likely to last."

Facebook lifted the temporary restrictions after a few days, she later said.

While aggressive online tactics threaten to divide a party desperate to avoid a repeat of 2016, the online enthusiasm Sanders inspires has been an asset for the Vermont independent, who is vying to compete against Trump, a reality television star with a devoted digital following.

“What are we going to do if Bernie isn’t the nominee? That’s a question every Democratic candidate should be thinking about,” said Keegan Goudiss, who directed digital advertising for Sanders’s 2016 campaign. “Whether or not the online conversation is real, there’s going to be division that’s stoked. That’s true no matter how emphatically Bernie says to support the nominee.

While the comparison to Trump’s online following is imperfect, Goudiss added, there are plainly parallels, above all the “cult of personality” energizing Americans distrustful of other politicians, as well as the projection of strength when they perceive their candidate to be under siege.

Over time, the focus of the meme-making energy has shifted. In January 2019, most of the critical images posted about other candidates by pages with “Bernie Sanders” or “Our Revolution” in their names focused on Sen. Kamala D. Harris (D-Calif.), according to Davis’s analysis. By October, still several months before Harris would exit the race, she’d faded away as a target.

Meanwhile, whereas Warren once commanded less than 10 percent of the attention, she is now the subject of nearly half of the disparaging memes, Davis’s research shows. Examples include a Photoshopped image of Warren in a dark wig. “With Booker gone,” the text reads, referring to Sen. Cory Booker of New Jersey, “I’m the only black candidate.” Another shows Warren taking a blade to Sanders’s back. Many mock her claims of Native American ancestry, which is also a common target for Trump and his allies.

A spokesman for the Warren campaign declined to comment. The rejoinder from her supporters has been oblique. Repurposing the serpent jibe, a “Snakes for Warren” account recently emerged on Twitter, with about 1,000 followers.

“There’s no fighting back against it; there’s only rolling with it,” said Misha Leybovich, a tech entrepreneur and former McKinsey consultant who has been organizing “Warren’s Meme Team,” a collection of supporters with no formal links to the campaign.

He downplayed the significance of the online onslaught, arguing, “The vast, vast majority of supporters of both Sanders and Warren, and all the other candidates, are great. Most of us just want to see Trump out of office."

But interviews with owners and administrators of the pro-Sanders groups present a more complex picture. Buck Bewley, who runs a repair shop near Louisville, Ky., would vote for Warren over Trump, but he has soured on the Massachusetts Democrat. So he let the disparaging meme of Warren’s visage as a mask for Clinton rack up views and shares in his group, the “Bernie Sanders Bernstorming Network."

“We get mad and post memes saying things that we probably wouldn’t say in real life,” said Bewley, 53. But he acknowledged how the Internet-stoked outrage could have unintended consequences, possibly estranging other Democrats from the Massachusetts senator.

Or, as he put it, “I think information is power. It’s a ripple effect on Facebook."

Julie Tate and Tony Romm contributed to this report.