But Rolling Stone spoke to multiple current and former Sanders aides who worry the Senator’s personality — he’s phobic about personal confrontation and retains traces of an inferiority complex from his days as an Independent straggler — might lead him to miss a chance at history. They say the campaign, which declined to comment for this story, has, among other things, declined to aggressively confront Joe Biden on issues like Social Security, trade, and the bankruptcy bill.

“Bernie is conflict-averse,” says Matt Stoller, who worked for Sanders for two years. “His staff has always had real trouble getting him to criticize any Democrat by name.”

“Bernie is always better on the counterpunch, on the rope-a-dope,” says Mark Longabaugh, who was chief strategist for Bernie’s 2016 campaign. “When he lands, it’s usually a counterpunch, like ‘I wrote the damn bill.’ It’s hard for him to go on the attack.”

“I always said, if he learned anything from 2016, it’s that in order to win the nomination, to beat the political establishment, you have to take it from their cold, dead hands. You have to go to war with these people,” the longtime former aide says. “But Bernie is acting like he’s running for State Senator in Burlington.”