While managing to avoid such blasé matters as our half-dozen Middle Eastern wars, the Democratic debate in Nevada on Wednesday evening did hit on the very important question of whether the supporters of Sen. Bernie Sanders (I-Vt.) are exceptionally mean on the internet.

In his most obvious whopper of the night, Sanders said "99.9 percent" of Twitter users are "decent human beings," then added that he "disown[s]" those who make ugly online attacks in his name. Former South Bend Mayor Pete Buttigieg wasn't satisfied. "Senator, when you say that you disown these attacks and you didn't personally direct them, I believe you," he responded. "But at a certain point, you got to ask yourself: Why did this pattern arise? Why is it especially the case among your supporters that this happens?" He went on to argue that leadership "is about what you draw out of people," and that if Sanders is, however unintentionally, motivating worse behavior than the other candidates, perhaps he is unfit to lead the country.

Let's set aside, for the sake of conversation, the debate over whether Sanders' supporters — "Bernie Bros," as the epithet goes — are truly substantially more vicious tweeters than any other political tribe. We'll simply acknowledge that some subset of his fans are very online and quite cruel to their political enemies. Is that Sanders' fault? Is it a mark on his leadership? More broadly, how much are politicians required to "own" the behavior and/or beliefs of the people who like them?

The bigger question is hardly unique to this election cycle, nor does it require consideration of internet etiquette. In the 2016 race, one of President Trump's unofficial endorsements came from The Crusader, a newspaper which calls itself "the premier voice of the white resistance" and is affiliated with the Ku Klux Klan. Former KKK leader David Duke also backed Trump, declaring that if he won his bid for a U.S. Senate seat (he did not), no other senator would "be more supportive of [Trump's] legislative agenda, his Supreme Court agenda."

After some initial hemming and hawing, Trump rejected both endorsements, denouncing Duke and issuing a campaign statement saying The Crusader "is repulsive and their views do not represent the tens of millions of Americans who are uniting behind our campaign."

More recently, Duke endorsed Rep. Tulsi Gabbard (D-Hawaii) for president in 2020, a backing she vehemently rejected. Republican lawmakers this past fall busily rid themselves of campaign contributions from Igor Fruman and and Lev Parnas, associates of presidential lawyer Rudy Giuliani who were indicted for "engaging in a scheme to funnel foreign money to candidates." And in the five years since Trump's campaign began and his crass, callous rhetoric became a constant feature of our news cycle, some research suggests school bullying has increased in pro-Trump districts and that some children explicitly adopt Trumpian language to harass their peers.

More serious are acts of violence with political motive. Think of the 2017 shooting in which a left-wing activist attacked Republican members of Congress, injuring Rep. Steve Scalise (R-La.) and several others. Or Cesar Sayoc, convicted of mailing pipe bombs to prominent Democrats and Trump critics in the media. Or the Florida man who this month drove a van into a GOP voter registration tent because, per his arrest report, he "does not like President Trump." Or The Guardian's compilation of 52 reported acts or threats of violence committed explicitly in Trump's name.

Do politicians' bear responsibility for these unwanted attentions? I don't think we can give a universal yes or no, but perhaps a few guidelines for parsing that responsibility may be drawn.

First, blanket condemnation of the candidates on the receiving end of unwanted endorsements from reprehensible people is unfair. In Gabbard's case, Duke explicitly indicated that the appeal he saw was her noninterventionist foreign policy, which has been central to her campaign. That appeal doesn't make Gabbard's foreign policy bad. It doesn't make her a white supremacist, because sometimes white supremacists like things that are not themselves white supremacist. (As I noted recently about a proposed executive order concerning federal building design, the fact that Nazis liked Greek columns doesn't make the columns inherently fascist.)

That said, Buttigieg's argument — that "at a certain point, you got to ask yourself: Why did this pattern arise?" — is fair. It may be that the answer, as with the Greek columns and Gabbard's foreign policy, is there's simply an innocent overlap for which the candidate deserves no blame.

Yet assignment of responsibility becomes increasingly justified if a more substantive connection exists, whether unknowingly or not. In Trump's case, the author of the Crusader article about Trump told The Washington Post the president's appeal was "his nationalist views and his words about shutting down the border to illegal aliens" — which is to say, the racists like him for race-related reasons. Likewise, Trump's history of praising violence against reporters and offering to pay the legal fees of supporters who fight protesters at his rallies creates a substantive connection between him and violence done in his name which cannot be so easily replicated with most public figures across the political spectrum.

Sanders' situation is tricky because it's not obvious there's a substantive connection (though Hillary Clinton and some of her supporters have argued it's shared sexism). He hasn't, to my knowledge, employed harsher or more malicious rhetoric than his Democratic rivals. On the contrary, he has repeatedly issued calls for civility. This is not, as with Trump and the schoolyard bullies, a case of the public parroting the politician.

To my mind, the likeliest explanation is that the younger voters Sanders attracts are more active online than other candidates' supporters, so their vitriol is both more traceable and less constrained by the norms of in-person interaction. That theory won't be confirmable without the data of several more election cycles. But as digital natives become an ever-larger portion of the voting public, having the dregs of your base embarrass you on the internet may become a given of modern politicking.

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