The campaign of Democratic presidential candidate Sen. Elizabeth Warren trolled Facebook on its own turf last week, stoking the debate about how aggressively the social media giant, whose massive reach was exploited during the 2016 elections, should tackle disinformation and political ads.

The Facebook page for Warren’s campaign ran an ad that intentionally opened with a piece of misinformation, “Breaking news: Mark Zuckerberg and Facebook just endorsed Donald Trump for re-election.”

“You’re probably shocked, and you might be thinking, ‘how could this possibly be true?’ ” it continues. Then comes the reveal.

“Well, it’s not. (Sorry.),” the ad continues. “But what Zuckerberg *has* done is given Donald Trump free rein to lie on his platform — and then to pay Facebook gobs of money to push out their lies to American voters."

Warren’s ad further claims that “if Trump tries to lie in a TV ad, most networks will refuse to air it. But Facebook just cashes Trump’s checks. Facebook already helped elect Donald Trump once. Now, they’re deliberately allowing a candidate to intentionally lie to the American people. It’s time to hold Mark Zuckerberg accountable — add your name if you agree.”

Warren’s campaign and Facebook’s communications team continued to spar on the subject — on Twitter — well into Saturday night.

Warren (D-Mass.) has called for Facebook to be broken up, an idea that founder Mark Zuckerberg did not like very much. And her latest shot at the platform has continued a debate on disinformation spread by politicians and whether traditional and social media companies have an obligation — or even a right — to curtail them.

Her campaign’s Facebook ad appeared to refer to the controversy surrounding a Trump campaign spot titled “Corruption,” which made false assertions about former vice president Joe Biden and claimed without evidence that the 2020 Democratic presidential contender offered $1 billion to Ukraine to help his son Hunter Biden. It also accused several prominent television journalists of supporting impeachment.

The ad ran as the president finds himself engulfed in scandal, after a whistleblower revealed that Trump appeared to ask Ukrainian President Volodymyr Zelensky to investigate the Bidens. Those revelations have led House Democrats to begin an impeachment inquiry.

PolitiFact rated the numerous claims made in the ad as “false,” and CNN refused to air that ad, as well as a second one, owing to its inaccuracies and attacks on journalists. The Biden campaign complained to Facebook about the ad, which the Trump campaign had promoted on the social network. Facebook, however, refused to take it down.

On Saturday night, Facebook’s communications team tagged Warren in a tweet defending the social media giant’s decision to keep the ad, with a new justification that it had also run on some television stations. The senator hit back, writing, “It’s up to you whether you take money to promote lies.”

Politicians are treated differently than other Facebook users when it come to making false claims on the platform, The Washington Post reported Thursday. Politicians’ statements are not subjected to the same fact-checking scrutiny that other advertisements typically go through, the vice president of global affairs and communications Nick Clegg said last month.

“We do not submit speech by politicians to our independent fact-checkers, and we generally allow it on the platform even when it would otherwise breach our normal content rules,” Clegg said. A subsequent post on Facebook’s website clarified that this policy covered “organic content or ads.”

Facebook’s rationale for not curtailing this content boils down to three points: that they fear encroachment on free speech; that these statements are often newsworthy; and that politicians are already fact-checked.

In a written response to the Biden campaign’s complaints, Katie Harbath, the platform’s public policy director for global elections, said that the company allowed such ads to stand because “our approach is grounded in Facebook’s fundamental belief in free expression, respect for the democratic process, and the belief that, in mature democracies with a free press, political speech is already arguably the most scrutinized speech there is.”

On Saturday, Facebook spokesman Andy Stone referred The Washington Post to Clegg’s and Harbath’s previous statements.

Of course, it’s not just Facebook that’s taking heat. Democrats such as presidential candidate Sen. Kamala D. Harris (D-Calif.) have called for Twitter to take action on Trump’s account, which he has used to share conspiracy theories and lodge racist and sexist attacks against political opponents. Twitter has long refused to do so.

The networks must thread a difficult needle: how to maintain the least toxic political discourse possible without taking actions that will anger privacy experts and free speech advocates, or trigger outrage from conservatives, who frequently allege that the social networks are biased against them.

But campaigns are spending millions of dollars to push these ads to millions of Americans, and citizens on both sides of the aisle are nervous about a repeat of 2016. Facebook has introduced new tools to make political advertising more transparent, including an Ad Library that documents every ad the campaigns and other political entities have run and how much they’re spending on the platform.

But controversies such as the one that has erupted over Trump’s ad suggest to critics that the platform isn’t doing enough to regulate digital campaigning in 2020. If the Trump campaign can claim that Joe Biden tried to give a billion-dollar bribe to Ukraine, then his potential opponents may be left to wonder: What else are they going to try?

Without any clear sense of where lines are on social media, politicians of both parties will likely continue to cross them. And in response, critics of the platform are likely to continue to push for greater accountability.

The controversial Trump ad in question is no longer running on Facebook. It expired on Oct. 6. But according to the Facebook Ad Library, the Trump campaign has since moved on to ads hawking “Where’s Hunter?” T-shirts.

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