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.