Read: The night socialism went mainstream

But many Democratic insiders remain deeply skeptical. Sanders’s support among party elites dramatically lags his support among Democratic voters. According to FiveThirtyEight’s Endorsement Tracker, which awards candidates points when party officials endorse them, Sanders ranks fourth in endorsement points, behind Bloomberg and Warren and far behind Biden. While ordinary voters don’t exhibit much hostility toward Sanders, party leaders do. When Seth Masket of the University of Denver interviewed Democratic activists in Iowa, New Hampshire, South Carolina, Nevada, and Washington, D.C., this month, he found that almost two-thirds said they feared a Sanders nomination. The only candidate who elicited a more negative response was Tulsi Gabbard, the representative from Hawaii who some Democrats fear will run a spoiler third-party campaign against the eventual nominee.

This animosity seeps into the mainstream media, where Democratic strategists often express their opinions, and inform the opinions of journalists who cover the presidential race. According to an In These Times study of MSNBC’s prime-time coverage, in August and September of last year, Sanders received less coverage than Biden and Warren, and the coverage he did receive was more negative. “The media keep falling in love,” the Washington Post media columnist Margaret Sullivan noted last week, “with anybody but Bernie Sanders.”

Democratic insiders tend to be institutionalists. They are more likely than ordinary voters to care about the fact that Sanders hasn’t always been a registered Democrat, that he often criticizes party officials, and that he didn’t do more to help Clinton in 2016. Masket told me that many of the party bigwigs he interviewed resented Sanders for “being a spoiler for 2016” by supposedly undermining Clinton, and for “sticking his finger in the eye of the Democratic establishment.”

The other reason Democratic insiders disproportionately oppose Sanders is that party elites and the journalists with whom they interact tend to distrust radicals of any stripe. “A quarter-century covering national politics has convinced me that the more pervasive force shaping coverage of Washington and elections is what might be thought of as centrist bias, flowing from reporters and sources alike,” the former Politico editor John Harris recently observed. “This bias is marked by an instinctual suspicion of anything suggesting ideological zealotry, an admiration for difference-splitting.” Pundits may not always express this fear of extremism as openly as MSNBC’s Chris Matthews did earlier this month, when his discussion of Sanders’s candidacy morphed into a broader indictment of socialism and of unspecified people who, Matthews said, would have cheered on “executions in Central Park” had “the Reds had won the Cold War.” But the centrist bias that Harris describes skews elite perceptions of public opinion. It keeps party and media insiders from recognizing that Bloomberg, a former Republican now running as a centrist, is a far more divisive figure among ordinary Democrats than the putatively radical Sanders.