Fake videos of Nancy Pelosi, slowed down to make her look drunk, are spreading on social media

Experts say it's a sign too many voters will easily believe misinformation campaigns ahead of the 2020 US presidential election.

Videos of US House Speaker Nancy Pelosi have been altered to make her appear drunk. Source: Twitter 'TraddyCath'

Videos distorted to make US House Speaker Nancy Pelosi appear drunk have been spreading across the internet. 

The videos, slowed down to give the impression Ms Pelosi is drunk - complete with slurred speech, long pauses and frequent eye closes - show her giving a speech at a Center for American Progress event.

During her speech, the Democrat said US President Donald Trump was guilty of a 'cover-up' because of his refusal to cooperate with congressional investigations.

Ms Pelosi only gave her speech on Wednesday, but one version posted by conservative political Facebook page 'Politics WatchDog' has already garnered 1.7 million views and 36,000 shares.

Seemingly unaware that the video had been altered, users commented "how many drinks did you have today" and "is she drunk or having a stroke?".

Very few users pointed out that the video had been doctored.

US President Donald Trump with House Speaker Nancy Pelosi. Source: AAP

Later analysis indicated the video had been slowed by about 25 per cent, with the person behind it also altering Ms Pelosi's pitch to hide any evidence of distortion.

Computer science and digital forensics professor from the University of California, Berkeley Hany Farid said there was "no question" the video had been tampered with.

"It is striking that such a simple manipulation can be so effective and believable to some," he told the Washington Post.

“While I think that deep-fake technology poses a real threat ... 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.”

Ms Pelosi is not the first victim of distorted videos have entered US politics. Last year, a video of CNN reporter Jim Acosta was altered to make it look like he had struck a White House intern when she tried to take a microphone back from him.

White House press secretary Sarah Huckabee Sanders then shared the video on the government's official press secretary Twitter page and did not remove it after learning it had been altered.