Supporters’ “bro-y” reputation took root during the 2016 election. The “Bernie Bro,” a term my colleague Robinson Meyer coined back in 2015 (not without regret), once referred to a member of a small band of Sanders devotees who were male, and well, kind of bro-y—they gave off an air of fratty masculinity. But the label quickly morphed into something much darker, used to describe someone who perpetrates (mostly) online harassment.

During the 2016 campaign, some Sanders supporters sent vile messages to female journalists, and threatened several writers and lawmakers. More recently, as the Times described, online followers went after a progressive activist who’d endorsed Senator Elizabeth Warren, and the father of a Parkland shooting victim who’d criticized Sanders’s position on guns. And earlier this month, Sanders fans across social media directed a flood of hostile memes and snake emojis toward Warren and her voters after she accused Sanders of saying a woman could not win the presidential election.

Sanders has denounced this kind of conduct. “I want to be clear that I condemn bullying and harassment of any kind and in any space,” he wrote in a letter to surrogates last year. Other than that message, though—which was echoed in the written guidance—the Sanders campaign has met the criticism with a kind of collective shrug. Any negative reputation that’s attached to Sanders’s supporters doesn’t appear to be having a significant impact on his electoral success, and the senator’s team is responding accordingly. “It’s very Twitter-focused, and it seems to be an issue that is largely weaponized online, rather than affecting people on the ground,” Briahna Joy Gray, Sanders’s national press secretary, told me.

“A kind of malaise that has emerged over the last 40 years with politics as usual creates real genuine frustration and real angst and real bitterness,” a senior adviser to Sanders, who requested anonymity in order to speak candidly, told me. “For [Sanders], there’s no reason to diminish or tamp down on an organic energy of dissatisfaction and frustration which he himself, I think, shares.” (Staffers have also suggested that Sanders’s people are being unfairly targeted, when fans of other candidates have participated in similar behavior.)

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Some of the Sanders backers I interviewed recently weren’t even aware of the extent of the criticism directed toward the candidate’s supporters. Outside the Ames rally last weekend, a mixture of curious Iowans and Sanders die-hards stood shivering in the cold as they waited to get inside the auditorium. There, I met Nick Moser, a college student from Granger, and I read him a few lines from Hillary Clinton’s recent interview with The Hollywood Reporter, in which she expressed reluctance to support Sanders as the Democratic nominee because of “his online Bernie Bros and their relentless attacks on lots of his competitors, particularly the women.” Granger raised his eyebrows. “I think that’s probably one of the dumbest things I’ve heard, in all honesty,” he said. His friend Grace Stackhouse, who plans to caucus for Warren next week, let out a laugh. “That’s a little bit broad of a statement to say about an entire group of supporters!”