Trump threatens to shut down social-media platforms after Twitter put a fact-check warning on his false tweets

President Donald Trump has threatened to close down social-media platforms that "silence" conservative voices.

He made the threat Wednesday, the morning after Twitter tagged some of his tweets with a fact-check warning.

The platform had been under pressure to take action after Trump leveled a groundless conspiracy theory against the MSNBC cohost Joe Scarborough.

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President Donald Trump has threatened to close down social-media platforms that he argues censor conservative voices after Twitter on Tuesday tagged some of his messages with a fact-check warning.

"Republicans feel that Social Media Platforms totally silence conservatives voices," Trump tweeted Wednesday. "We will strongly regulate, or close them down, before we can ever allow this to happen. We saw what they attempted to do, and failed, in 2016."

Twitter had long been criticized for allowing the president to spread conspiracy theories and smears against opponents despite its policies against the promotion of disinformation.

It recently came under increasing calls for it to take action against Trump after he spent weeks promoting a baseless conspiracy theory alleging that the MSNBC cohost Joe Scarborough was involved in the death of a staffer, Lori Klausutis, while he was serving as a US congressman.

Twitter has declined to take action against the president for the messages about Scarborough, but on Tuesday for the first time it put a fact-check tag on some of Trump's tweets.

The president wrote two tweets claiming "There is NO WAY (ZERO!) that Mail-In Ballots will be anything less than substantially fraudulent."

Twitter tagged each of the two messages with a blue exclamation mark and warning message, linking to articles in The Washington Post, CNN, and other outlets that debunk the president's assertion.

Trump doubled down on his voter-fraud claims in a follow-up tweet Wednesday.

"We can't let a more sophisticated version of that happen again," Trump wrote. "Just like we can't let large scale Mail-In Ballots take root in our Country. It would be a free for all on cheating, forgery and the theft of Ballots. Whoever cheated the most would win. Likewise, Social Media. Clean up your act, NOW!!!!"

Carl Tobias, a law professor at the University of Richmond, Virginia, said that Trump was unlikely to be able to follow through on his threat against social media companies.

"I think that it is mostly bluster. There are steps he might take, but they are likely to be slow, cumbersome and ineffective, although he does have the huge bullhorn of the presidency to persuade the voters that he is correct and deserves reelection," he explained to Business Insider by email.

"He could issue executive orders or try to persuade federal agencies to regulate or take action against Twitter or convince Congress to legislate, but none will be fast or help him before November," he expalined. "Reelection might help him achieve some of what he wants in the longer term as agencies and Congress are investigating big tech and may consider legislation but nothing will pass soon."

Trump has long accused social-media companies of bias against conservatives. In June 2019 he invited several far-right provocateurs and conspiracy theorists, some of whom had had hate speech removed by social-media platforms, to the White House for a social-media summit.

He has also credited being able to communicate on Twitter as a key factor in his election to the White House, remarking that it allows him to communicate with voters directly, unfiltered by media organizations he accuses of partisan bias.