Distorted videos of House Speaker Nancy Pelosi altered to make her sound as if she’s drunkenly slurring her words, are spreading rapidly across social media, highlighting how political disinformation that clouds public understanding can now spread at the speed of the web.

The video of Ms Pelosi’s onstage speech on Wednesday at a Centre for American Progress event, in which she said President Donald Trump’s refusal to cooperate with congressional investigations was tantamount to a “coverup”, was subtly edited to make her voice sound garbled and warped.

It was then circulated widely across Twitter, YouTube and Facebook.

One version, posted by the conservative Facebook page Politics WatchDog, has been viewed more than 2.3 million times by Friday morning, been shared more than 46,000 times, and garnered 25,000 comments with users calling her “drunk” and “a babbling mess”.

The origin of the altered video remains unclear but its spread across social media comes amid a growing feud between congressional Democrats and President Trump.

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In addition to links from multiple YouTube and Twitter accounts, the video has appeared in the comments sections of message boards and regional news outlets.

On Thursday night, President Trump tweeted a separate video of Ms Pelosi – a selectively edited super-cut, taken from Fox News, focused on moments where she briefly paused or stumbled – that he claimed showed her stammering through a news conference.

The clip included roughly 30 seconds of Ms Pelosi’s full 21-minute briefing on Thursday, in which she took questions from reporters and discussed what she called Trump’s “temper tantrum”.

Analyses of the distorted Centre for American Progress video by Washington Post journalists and outside researchers indicate that the video has been slowed to about 75 percent of its original speed.

To possibly correct for how that speed change would deepen her tone, the video also appears to have been altered to modify her pitch, to more closely resemble the sound of her natural speech.

The altered video’s dissemination highlights the subtle way that viral misinformation could shape public understanding in the run-up to the 2020 election.

Spreaders of misinformation don’t need sophisticated technology to go viral: even simple, crude manipulations can be used to undermine an opponent or score political points.

Clipping politicians’ speech into videos designed to undermine or embarrass them is nothing new.

But the outright altering of sound and visuals signals a concerning new step for falsified news, as presidential campaigns and their supporters battle to boost political messages and influence people online.

“There is no question that the video has been slowed to alter Pelosi’s voice,” said Hany Farid, a computer-science professor and digital-forensics expert at University of California, Berkeley.

“It is striking that such a simple manipulation can be so effective and believable to some,” he added.

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“While I think that deepfake technology poses a real threat,” he said, in reference to more sophisticated computer-altered videos, “this type of low-tech fake shows that there is a larger threat of misinformation campaigns – too many of us are willing to believe the worst in people that we disagree with.”

Owners of the Politics WatchDog page and representatives from Facebook and Twitter did not respond to requests for comment. Ms Pelosi’s office declined to comment.

YouTube spokesman Farshad Shadloo said the Pelosi videos violated company policies and have been removed. They did not appear prominently on the site, he added, and searches for Pelosi-related videos surface content from more authoritative sources.

Ms Pelosi’s voice was distorted in a separate YouTube video, posted earlier this month by a conservative channel with more than 28 million total views.

That video slowed a speech Ms Pelosi had given to the American Road & Transportation Builders Association to make her words sound notably slurred.

That video appeared to be a version of another video with roughly 200,000 views, in which a man laughed over of a spliced montage of her speech. The original audio shows no such distortion.

Such minor manipulations have become a growing obstacle for covering and understanding Washington.

In November, a video of CNN reporter Jim Acosta holding onto a microphone while a White House intern attempted to retrieve it was subtly altered to make the altercation look more dramatic.

The edited clip, originally shared by a creator of conspiracy-theory videos, was then shared widely across social media, including by White House press secretary Sarah Sanders.

Ms Pelosi has been the target of similar efforts before.

A video last year from The Next News Network, a conservative YouTube channel with more than 1 million subscribers, said Ms Pelosi was “fumbling” her speech because she was drunk or “pretty sick”. The channel’s owner did not respond to requests for comment.

A YouTube channel called The American Mirror posted a video saying Ms Pelosi garbled her words and suffered an “awkward 5-second brain freeze” at a speech earlier this month.

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That channel, which is almost entirely dedicated to videos crafted to criticise or embarrass female Democratic leaders such as Ms Pelosi and Hillary Clinton, has more than 30 million total views.

Kyle Olson, who runs the channel, said he found it “interesting” that “not a single reporter asks any questions when she suffers brain freezes”.

The videos, he added, “get hundreds of thousands of views because they speak for themselves: there is something not right with her”.

Ms Pelosi’s deputy chief of staff Drew Hammill said: ”We’re not going to comment on this sexist trash.”