Yang made his startling claim in the aftermath of the Nevada debate, attributing the claim to one of his own previous donors who he said heard Bloomberg’s plea first-hand.

“You heard this or know this?” Chris Cuomo said, jumping in.
“I heard it from a major donor,” Yang replied.
“Your donor?” Bash asked.
“Yes,” Yang confirmed. “A donor said that. And it’s a person who donates to a number of candidates, ordinarily, says these are the phone calls that Mike’s been making.”

Looking at these poll trackers, we see Bloomberg's rise is directly due to siphoning votes away from Joe:

https://projects.economist.com/democratic-primaries-2020/

https://projects.fivethirtyeight.com/polls/president-primary-d/national/

"Biden’s frustrated Bloomberg, who wasn’t that close w/ @BarackObama, has created impression thru clever, ubiquitous ads that 44 has endorsed him, which he has not."

So far, primary season contenders vying to unite the left and middle have flopped. Heading into Nevada, the Massachusetts senator is gambling she can break that streak.

Beto O'Rourke tried it. Kamala Harris tried it. Cory Booker tried it. And one by one, they all flamed out. Now, Elizabeth Warren is pitching herself as the Democratic candidate who can unify the party's progressive and moderate wings, a play that could lead her down the same bridge to nowhere, unless her message can quickly find some resonance.

The Massachusetts senator has pleaded with voters not to pick a divisive nominee who risks paving the way for President Donald Trump's re-election, telling a devoted crowd of supporters Tuesday in Manchester, New Hampshire, that she was Democrats' "best chance" of marshaling "a unified party" to the voting booths come November.

"The problem that Warren has is all of the Bernie people think she's a neoliberal shill and all of the centrists think she's a raging Maoist," said Sean McElwee, a left-wing organizer and analyst at Data For Progress whose work has been cited by the Warren campaign. "The people who want 'Medicare for All' don't believe she wants it, and the people who don’t want Medicare for All do believe she wants it."

Former Vice President Joe Biden and Minnesota Sen. Amy Klobuchar took aim Sunday at former New York City Mayor Michael Bloomberg ahead of this week’s Democratic presidential debate.

Bloomberg hasn’t yet qualified for Wednesday’s NBC News and MSNBC debate in Las Vegas, but has through Tuesday to meet the party’s criteria.

With that potential clash looming, both Biden and Klobuchar criticized Bloomberg in interviews with “Meet the Press” at a time when the former mayor faces increased scrutiny over past comments about race, policing and women at his eponymous company.

“$60 billion can buy you a lot of advertising, but it can't erase your record. There's a lot to talk about with Michael Bloomberg,” Biden said, approximating Bloomberg’s net worth.

“You take a look at the stop-and-frisk proposals. You take a look at his ideas on redlining he's talking about. You take a look at what he's done relative to the African American community. I'm anxious to debate Michael on the issues relating to, you know, what we're going to face in Super Tuesday.”

“It's going to be awful hard to go out and win those — the base support of the Democratic party, the African Americans, Latinos and working class white folks, and put that coalition together. That's how you win an election. You put that coalition together,” he added.

https://www.nbcnews.com/politics/meet-the-press/biden-klobuchar-hit-bloomberg-s-record-ahead-nevada-debate-n1137506