Joe Biden says Sanders-supporting “Bernie Brothers” are ramping up an increasingly negative campaign, after the former vice president’s White House shot was dramatically resurrected on Super Tuesday.

As support for his campaign surged – bringing in $22m (£17m) in just five days – he surged past the Vermont senator, a self-described democratic socialist, in the race for delegates for the Democratic nomination.

At a Maryland fundraiser, Mr Biden reportedly said: “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.

“We can’t tear this party apart and re-elect Trump,” he added. “We have to keep our eyes on the ball, in my view.”

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“Bernie Bros” has been the colloquial term for hardline Sanders supporters since the 2016 election cycle, where they have employed aggressive tactics on Twitter and other social media platforms.

But Mr Sanders’s communications director Mike Casca hit back, saying: “Tens of millions are uninsured while coronavirus spreads, the planet is warming at an accelerating rate, working people haven’t seen a real raise in decades, and Joe Biden is worried about some damn tweets?”

“Let’s try to stay focused on the big issues,” he added.

The next round of primaries take place on Tuesday, with Michigan, Washington state, Missouri, Mississippi, Idaho and North Dakota all voting.