Democratic presidential candidate Bernie Sanders discussed race relations, jobs, and campaign reform during a campaign stop in South Carolina amid rising poll numbers. (Reuters)

The presidential campaign of Bernie Sanders said Thursday that it had raised more than $1.2 million online in 48 hours after research surfaced from a super PAC backing Hillary Rodham Clinton that linked the Vermont senator to the “extreme” views of Jeremy Corbyn, the new leader of the United Kingdom's Labour Party.

The publication of the research by Correct the Record, a pro-Clinton group, prompted a fundraising solicitation Tuesday by Sanders that said he had been “pretty viciously” attacked and asked supporters for $3 contributions to “send a powerful message that we had have had ENOUGH of the billionaire class buying elections.”

The burst of money Sanders received online was unprecedented, according to a statement Thursday by Erin Hill, executive director of ActBlue, an online fundraising service used by Sanders and scores of Democrats.

“At one point, it drove 180 contributions through our platform per minute,” Hill said in the statement released by the Sanders campaign.

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The Correct the Record research was sent by e-mail to the Huffington Post and was apparently intended to be off the record. But its content was published anyway, the publication said, because it never agreed to those terms.

According to the Huffington Post, the pro-Clinton PAC sought in its e-mail to link Sanders to some controversial remarks made by Corbyn, including his praise for the late Hugo Chavez, the Venezuelan leader who provided discounted fuel to Vermont in a deal supported by Sanders. The research also cited Corbyn’s suggestion that the assassination of Osama bin Laden was "a tragedy," because there was no attempt to arrest and put the al-Qaeda leader on trial.

In his fundraising solicitation, Sanders said that the pro-Clinton PAC “suggested I’d be friendly with Middle East terrorist organizations, and even tried to link me to a dead communist dictator.”

"It was the kind of onslaught I expected to see from the Koch Brothers or Sheldon Adelson,” Sanders said, characterizing the move as an attempt “to stop the momentum of the political revolution we’re building together."

Following Corbyn’s recent election, Sanders, a self-described democratic socialist, said he was “delighted” by his ascendancy, citing their shared views on income and wealth inequality.

[A hands-off Democratic race: Clinton, Sanders won’t speak ill of each other]

Clinton and Sanders have generally avoided attacking one another directly, a dynamic that is very different from the campaign for the Republican nomination.

During the first quarter of the year, Sanders raised about $15 million for his campaign, a figure that exceeded expectations for a candidate originally written off a curiosity. Campaign aides have said they are continuing to raise money at a surprising clip.

Clinton, meanwhile, raised about $47 million, while an additional $24 million was raised by a trio of outside groups supporting her, including Correct the Record. Sanders has said repeatedly that he does not want the support of a super PAC.