That hasn’t stopped the chatter in Congress.

“I think Sanders is a problem for some moderates. There’s no question about it because I hear the talk around,” Democratic Representative Al Lawson, who represents a safe Florida district, said.

Allies of Sanders dismiss the angst as part of winnowing process in the primaries. They say that if the goal is defeating Trump, the party will coalesce around the nominee.

“There will always be concerns about party unity no matter who it is,” Ocasio-Cortez said. “Like, if Klobuchar or whomever were the front-runner right now, there would be a lot of stress as to whether progressives would unify” behind her.

Expanding the Field
Washington Representative Pramila Jayapal, a Sanders supporter and co-chair of the Congressional Progressive Caucus, said Democrats repeatedly make the mistake of picking moderate candidates who end up alienating the more liberal base of the party and losing the election.

“We can’t keep doing the same thing and expect a different result,” Jayapal said. “We are in this situation because we did not expand the electorate and nominate someone the voters actually trust.”

Sanders maintains a loyal base of supporters and has a proven ability to bring out youthful and working-class voters. Also, polls show him performing about as well as moderates Biden and Bloomberg in head-to-head match-ups against Trump.

Four years ago, establishment Republicans had similar concerns about their prospects in congressional races when it became clear that Trump would be their nominee. They still emerged with control of both the House and Senate despite a net loss of two Senate seats and six House seats.

‘Ballot Carnage’
As he attempts to claw his way back into contention, Biden has tried to stoke the concerns about the impact of a Sanders nomination on House and Senate races.

“Elected officials across the country understand that there would be down-ballot carnage for the Democratic Party if we nominated the wrong person,” Biden said Thursday on ABC’s “The View.” “And if Bernie Sanders was at the top of the ticket, we would be in jeopardy of losing the House. We would not get the Senate back.”

Republicans have been eager to stoke the divisions.

“He’s a socialist who would destroy the economy,” Iowa Republican Senator Joni Ernst, who is up for re-election in November, said. “I think he helps everyone up and down the ticket,” she said of GOP candidates.

House Republican leader Kevin McCarthy of California on Thursday also goaded Democrats over Sanders.

“Think about what would be his cabinet -- AOC? Tlaib? Omar?” he said referring to Ocasio-Cortez, Michigan’s Rashida Tlaib and Minnesota’s Ilhan Omar, the self-described squad of first-term progressives who have been particular targets of Trump and Republicans.