Joe Biden warned a group of high-dollar donors that rabid online Bernie Sanders fans will try to make the 2020 Democratic primary nasty, in the process mangling the "Bernie bros" nickname bestowed on the Vermont senator's most vocal male supporters.

“What we can’t let happen is let this primary become a negative bloodbath. I know I’m going to get a lot of suggestions on how to respond to what I suspect will be an increasingly negative campaign that the Bernie brothers will run," the former vice president said Friday by phone to a group of about 130 donors in the Washington, D.C., suburb of Bethesda, Maryland, according to a pool report. He lengthened the common "Bernie bros" nickname for online fans of the Vermont senator.

"We can’t tear this party apart and reelect Trump. We have to keep our eyes on the ball, in my view," Biden said.

Biden, 77, said he raised $22 million in the last five days and said that after a polling data briefing, his campaign feels "awfully, awfully good" about the next primaries on Tuesday, including Michigan, Missouri, Mississippi, and Washington state, "where Bernie was predicted to walk away with it.”

Sanders's aggressive internet army was the subject of criticism in recent Democratic presidential debates. Sanders said that he will " disown" those "who make ugly remarks."

Massachusetts Sen. Elizabeth Warren, who dropped out of the race following a poor Super Tuesday showing, lamented Sanders supporters' "organized nastiness” in an interview Thursday, adding that candidates "are responsible for the people who claim to be our supporters and do really threatening, ugly, dangerous things to other candidates."

“It’s going to be hard, this guy’s going to come at me, and throw everything, including the kitchen sink. I don’t mean Bernie, I mean in the general election. But Bernie is going to throw, he's at least throw the dishwasher at me,” Biden said with a laugh. “We’re going to be OK. I just have to keep steady and moving forward and just laying out what we’re going to be talking about in a coherent way.”