Elon Musk said on Twitter on Saturday that he would reinstate former President Donald J. Trump to the platform as part of a shake-up of the social media service, with Mr. Trump’s account quickly showing up again on the site.
Mr. Musk, who bought Twitter for $44 billion last month, had asked users on the platform starting late Friday afternoon about whether to allow Mr. Trump back onto the service. Twitter had barred Mr. Trump after the riot on Jan. 6, 2021, at the U.S. Capitol, saying his posts had run the risk of inciting violence.
More than 15 million votes were logged in answer to Mr. Musk’s question about whether to reinstate Mr. Trump, according to the results that Mr. Musk included in his tweet, with nearly 52 percent in favor of the former president returning to Twitter. Mr. Trump’s Twitter account went live shortly after, though the former president’s last tweet was from Jan. 8, 2021.
“The people have spoken,” Mr. Musk said on Twitter. “Trump will be reinstated.” He added the Latin phrase “Vox Populi, Vox Dei,” which roughly means that the voice of the people is the voice of God.
Mr. Musk and Twitter did not immediately return requests for comment.
Mr. Trump, who did not immediately return a request for comment, had announced on Tuesday that he planned to seek the White House again in 2024. Whether Mr. Trump will agree to return to Twitter is not clear. He has started his own social network, Truth Social, in which he has a financial stake.
Mr. Trump is obligated to make his posts available exclusively on Truth Social for six hours before sharing them on other sites, according to a filing with the Securities and Exchange Commission. He can post to any site immediately if the messages pertain to political messaging, fund-raising, or get-out-the-vote initiatives. Truth Social did not return a request for comment.
“I like Elon, but I’m staying on Truth,” Mr. Trump said during a Fox News interview after Mr. Musk’s takeover.
It was also unclear if Mr. Musk would stick with his decision to allow Mr. Trump’s account back on Twitter. Since buying the company, Mr. Musk has upended it and changed course several times, slashing its onetime 7,500-person work force, pushing to develop new products and changing his mind about what content to allow on the platform.
Mr. Musk, a longtime self-described “free speech absolutist,” had said in May that he would reverse the permanent ban of Mr. Trump on Twitter and let him back on the social network. But Mr. Musk had hit pause on changing Twitter’s content rules after completing his buyout.
Late last month, he said that Twitter would form a content moderation council to handle major content decisions on the platform and that he would not make any moves on account reinstatements “before that council convenes.” No council has been formed. Then on Friday, Mr. Musk had tweeted that he was allowing some people whose Twitter accounts had been barred, including the comedian Kathy Griffin and the author and psychologist Jordan Peterson, back on to the platform.
Alex Stamos, the director of the Stanford Internet Observatory, said it was “odd” that Mr. Musk, who has spent months complaining about Twitter’s problem with bot accounts, would use a Twitter poll in which bots could be voting to decide the issue and then assume that the result “reflects some kind of legitimate ‘voice of the people.’”
“It is definitely possible for small groups to create large numbers of accounts to manipulate features like polls,” he added.
Mr. Trump’s Twitter reinstatement raised immediate concerns from misinformation experts and others. The former president had used Twitter as a megaphone during his presidency to praise, cajole, lobby and put forward his version of events. He often spread inaccurate information and occasionally announced policies on Twitter even before his own staff had been told. Before the 2020 presidential election, Mr. Trump had also tweeted comments that sowed doubt about the integrity of the vote.
If Mr. Trump reverts to the same kind of content that he has been sharing on Truth Social, he could make Twitter a “hotbed of hate, harassment and incitement,” said Joan Donovan, the research director at Harvard’s Shorenstein Center on Media, Politics and Public Policy, which has studied the proliferation of misinformation.
If Mr. Trump returned to Twitter, it was also likely to be a boost for his personal brand because he could now reach a far wider and more influential audience, she said.
“The difference between Twitter and Truth Social isn’t just a matter of degree. It’s a matter of influence — global leaders, journalists, technologists, celebrities, culture makers, these are the people that are on Twitter,” Ms. Donovan said. Even if Mr. Trump simply tweets links to his posts on Truth Social, it would bolster his brand, she said.
Conservatives cheered Mr. Musk’s decision, saying it was a victory for the freedom of speech. The phrase “He’s Back” was trending on the platform on Saturday evening.
“Elon Musk reinstating Donald Trump’s Twitter account is a middle finger to all of mainstream media, woke leftists & Big Tech,” tweeted Steven Crowder, a conservative commentator. “If you claim to support free speech, this should have you smiling from ear to ear.”
Mr. Trump has vacillated in his opinions of Mr. Musk. In July at a rally in Alaska, he called Mr. Musk an insulting term for apparently supporting his political opponents in the 2016 and 2020 elections even though, Mr. Trump said, “He told me he voted for me.” Mr. Trump also said that Mr. Musk, who was trying to back out of his agreement to buy Twitter at the time, “got a pretty rotten contract.”
But last month when Mr. Musk closed his acquisition of Twitter, Mr. Trump declared himself “very happy that Twitter is now in sane hands.” In a post on Truth Social at the time, Mr. Trump added that he was glad Twitter “will no longer be run by Radical Left Lunatics and Maniacs that truly hate our country.”
The return of Mr. Trump’s account could further deter Twitter’s advertisers, which provide the bulk of the revenue for the social media company. General Motors and other brands paused their spending on Twitter after Mr. Musk’s takeover of the company, especially as a new system that allowed anyone to pay for a check mark to verify their account caused chaos.
Critics of Mr. Musk’s decision immediately began lobbying advertisers to take the opportunity to depart.
“Any advertiser still funding Twitter should immediately pause all advertising,” Derrick Johnson, the president of the N.A.A.C.P., said in a statement.
He added, “In Elon Musk’s Twittersphere, you can incite an insurrection at the U.S. Capitol, which led to the deaths of multiple people, and still be allowed to spew hate speech and violent conspiracies on his platform.”