On Monday, Media Matters, a progressive media watchdog organization, warned that Musk taking over Twitter would result in the return of Donald Trump to the platform, and open the gates for extremists and white supremacists.

“The sale of Twitter to Elon Musk would be a victory for disinformation and the people who peddle it,” said Angelo Carusone, president of Media Matters, in a statement. “Musk could unleash a wave of toxicity and harassment and undo Twitter’s efforts to increase quality engagement and make its platform safer for users.”

Carusone predicts Trump, who received a lifetime ban from Twitter on Jan. 8, 2021, following the insurrection at the U.S. Capitol, would be back on the platform “within weeks.”

Republicans in the U.S. House and elsewhere, however, are celebrating a possible Musk deal with Twitter and hoping a takeover by the Tesla CEO would reverse the decision that led to Trump’s ouster from Twitter. On Monday, a group representing 209 House Republicans called for exactly that:

Trump’s family has also hinted at a possible return.

“We’ll see what it means for my father-in-law, but the fact that you have terrorist organizations that have been allowed to stay on Twitter, but the former president of the United States still is not on there: absolutely outrageous,” said Lara Trump, a Fox News contributor and wife of Donald’s son Eric Trump, when Musk initially made his bid. “Although he’s got other plans working right now, I don’t know if he’ll carry the way, but I bet there are millions of Americans who would like to see him back.”

Twitter, when banning Trump, cited “the risk of further incitement of violence” as the reason behind the decision.

Trump, in the days before he was banned from Twitter, stated that he would not attend the inauguration of President-elect Joe Biden, and referred to his supporters as “American Patriots,” saying they will have “a GIANT VOICE long into the future.” Twitter said at the time those statements were “likely to inspire others to replicate the violent acts that took place on January 6, 2021, and that there are multiple indicators that they are being received and understood as encouragement to do so.”

Trump’s not the only right-wing politician who could return to Twitter after a ban, either. U.S. Representative Marjorie Taylor Greene had her personal account banned after violating the company’s COVID-19 misinformation policy, but began lobbying Monday for that to be reversed via her Congressional feed.

Media Matters is urging Twitter’s board to negotiate certain terms into any possible deal with Musk that would uphold existing community standards, including the removal of people who violate them.

“Handing Musk the reins to Twitter will undoubtedly unleash the conspiracy theories that platform has attempted to squelch, and any attempt to use the platform for legitimate information sharing will be overshadowed by a toxic cesspool of misinformation,” said Carusone. “The only thing worse than Twitter replatforming the likes of Donald Trump and Alex Jones—as well as reversing course in dealing with disinformation and extremists—is the perverse pressure it’ll create on other major social media platforms, effectively igniting a race to the bottom.”

Musk’s biggest promise, if he takes over Twitter, is to transform it into a platform for free speech with few restrictions—something he calls “essential to a functioning democracy.” He has previously referred to himself as a “free-speech absolutist.”

“I believe free speech is a societal imperative for a functioning democracy,” Musk wrote earlier this month. “However, since making my [initial Twitter] investment I now realize the company will neither thrive nor serve this societal imperative in its current form. Twitter needs to be transformed as a private company.”