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

The video of Pelosi’s onstage speech Wednesday at a Center 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, had been viewed more than 2.5 million times by Friday evening.

The origin of the altered video remains unclear, but its spread across social media comes amid a growing feud between congressional Democrats and Trump. 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 Donald Trump tweeted a separate video of Pelosi — a selectively edited supercut, 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 Pelosi’s full 21-minute briefing on Thursday, in which she took questions from reporters and discussed what she called Trump’s “temper tantrum.”

The altered Center for American Progress 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 the University of California, Berkeley.

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

Pelosi has been the target of similar efforts before.

Her 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 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.