Three members of his team didn’t even back Hillary Clinton, the Democratic nominee, and instead supported the Green Party in the general election.
Others have made a career of ripping the very people Mr. Sanders now faces in the 2020 Democratic primaries.
Among those is David Sirota, his senior adviser and speechwriter who has earned a reputation for combativeness online. He has deleted 20,000 of his tweets, many of them harsh attacks on other Democrats, according to Politico.
Mr. Sirota and the other political warriors seem to belie the image the septuagenarian socialist enjoys among the voting public.
"These people are attack dogs and make it look like Bernie’s planning on a slash-and-burn campaign," said one longtime Democratic operative with deep presidential campaign experience. "Either Bernie’s naive, which I don’t think he is, or it’s a little bit of a recognition I’m going to say one thing and do the complete opposite."