A message saying you "won't be safe" in Joe Biden's America. The former vice president shown "sleeping" during a television interview. Biden "hiding" -- alone -- in his basement.

All three videos featured in social media of President Donald Trump and his team as recently as the past week as he sought to close the gap on his Democratic rival. And each was labeled as false or manipulated content by social media giants and fact checkers.

While negative campaigning has long been a fixture of American politics, the open use of digitally-altered images by Trump and other candidates in 2020 has tech giants worried.

Twitter has cracked down by removing or labeling several of the president's tweets. Facebook, citing the risk of civil unrest, announced Thursday that it would not allow new political ads on its platform in the last week of the November 3 race.

There remain questions whether such messages -- almost impossible to stop once they become viral -- are working on voters but a line has already been crossed.

"There's a long tradition in politics of competing politicians presenting their opponents' words or beliefs in edited ways, right? That's part of politics," Ethan Porter, assistant professor of media and public affairs at George Washington University, told AFP.

"On the other hand, the Trump campaign is in part running a campaign entirely detached from reality, in ways that have little to no precedent in American political history."

Biden's campaign has yet to receive the same kind of censure as Trump's. But can a willingness to manipulate highly visible political ads and videos produce results? 

The Real Clear Politics poll average barely changed after the Republican Convention, where Trump ramped up his attacks on Biden who is seven points ahead nationally. But swing states remain a toss-up.

'One-sided' 

"Manipulated media for the most part has been used by the Trump campaign to try and have more, let's say, 'tactile-looking' evidence, for the claims that they're making. Because there's not actual evidence," said Shannon McGregor, an assistant professor at the Hussman School of Journalism and Media, University of North Carolina, Chapel Hill.

It's similar to the approach used in 2016, but technology has made manipulations easier and more sophisticated.

The Trump campaign accused tech companies of double standards over the Biden videos.

"Big tech is in Joe Biden's pocket but the liberal coastal elites in Silicon Valley are blatantly one-sided when it comes to how they define manipulated media," Samantha Zager, deputy national press secretary, told AFP.

However, McGregor, who studies the role of social media in political processes, said that rather than aiming to attract different constituencies, "the rhetoric is really polarizing and it's sort of digging into Trump's base of supporters and trying to activate them to vote."

An example came in an August 30 Facebook post by Donald Trump Jr, after the shooting death of Aaron Danielson, 39, in Portland.

"WARNING, HORROR: Antifa Targets And Executes Trump Supporter," the president's eldest son said in his post, which included video that was viewed more than 780,000 times, and liked almost 50,000 times.

A suspect said to be a supporter of the Antifa anti-fascist movement was shot and killed on Thursday night as police tried to arrest him.

'Drinking their Kool-Aid' 

The violence in Portland came just before Facebook boss Mark Zuckerberg announced the restrictions on political ads, saying misinformation about mail-in voting, and concerns about delayed counting of ballots, meant the 2020 election is not business as usual.

Porter said the Trump team is convinced its approach is a winner.

"In some ways they seem to have drunk their own Kool-Aid. They believe that their social media use and strategy in 2016 won them the election," he said.

"It's not to say he won't win. It's just to say that if he does win I can't imagine that will be one of the top or most likely causes," Porter added, maintaining that fact-checking of false information does work.

Cyrus Krohn, who managed digital campaigning for the Republican National Committee ahead of the 2008 election, says this year's race "does appear to be tightening" and "you can attribute that to the fear factor that the internet is creating."

That means, he said, that manipulated media are working for the Trump team. Although the Biden campaign is not "as overt," Krohn said, "there are factions on the left who would like to see the (former) vice president elected that are deploying the same tactics as the official Trump campaign."