Zuckerberg later shared the report on social media, saying it provided "an unfiltered version of what I'm thinking and telling employees on a bunch of topics" including "breaking up tech companies."

The remarks quickly drew a rebuke from the progressive firebrand, who fired back on Twitter: “What would really ‘suck’ is if we don’t fix a corrupt system that lets giant companies like Facebook engage in illegal anticompetitive practices, stomp on consumer privacy rights, and repeatedly fumble their responsibility to protect our democracy.”

The dust-up comes as the 2020 election season heats up and questions linger over whether Facebook is up to the task of combating political misinformation after failing to curb a Russian campaign to meddle in the 2016 U.S. presidential election. Perceived hostility to a major Democratic candidate could exacerbate tensions between Facebook and a party that once viewed the company and its Silicon Valley peers as bastions of American innovation.

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And it marks the most direct public skirmish between Warren and Zuckerberg since the Massachusetts lawmaker unveiled her campaign plan to split up the company. Warren ignited fresh debate over whether Facebook and other tech giants have grown too big and powerful with that March proposal, which would force Zuckerberg's company to spin off its two biggest acquisitions: Instagram and WhatsApp. Since then, other 2020 Democratic hopefuls have piled on with calls for federal regulators to either investigate tech giants for anti-competitive conduct or to outright dismantle them.

The calls reflect Silicon Valley's shifting headwinds in Washington, which increasingly views the industry as under-regulated and over-concentrated. Democrats and Republicans alike are increasingly calling for lawmakers in Congress and regulators at the Justice Department and Federal Trade Commission to rein in tech titans like Facebook, Google and Amazon.

Under the Trump administration, both agencies have in fact launched antitrust probes of major tech companies, though it's not yet clear if those will lead to firm action. Democrats scoffed at recent FTC fines that resolved privacy investigations into Facebook and Google's YouTube, contending Trump's chosen regulators are failing to hold tech accountable for misdeeds despite the sharp rhetoric aimed at the industry.

Warren was one of those voices, tying her critiques to her central argument that tech's power and size pose myriad consumer harms. Allies in Warren's crusade on tech say Zuckerberg's candid remarks to staffers validate her approach.

“A hallmark of Warren’s career has been challenging corporate power on behalf of regular people, and this just serves as a real validator that she’s a real threat to both Wall Street executives and tech moguls," said Adam Green, co-founder of the Progressive Change Campaign Committee.

Stacy Mitchell, co-director of the Institute for Local Self-Reliance and a proponent of Warren's plan to break up Facebook, said the audio also served to thrust the debate over tech and antitrust back into the campaign limelight.

"Zuckerberg’s leaked comments remind people that the federal government has potent legal tools to rein these giants in, if enforcement officials opted to use them," Mitchell told POLITICO. "He’s helping to ensure that monopoly policy continues to be a standout issue in this election."

The shift in sentiment towards the company began in the wake of the Cambridge Analytica privacy scandal and after it was revealed that Facebook was a primary platform for Russia's disinformation campaign during the 2016 election. Since, the company has vowed to tighten restrictions that protect its consumers from privacy violations and election interference, but lawmakers on both sides of the aisle maintain that those policies aren’t enough.

Zuckerberg in particular has faced personal pressure to testify before government panels in the U.S. and abroad to face questions about the company's handling of users' personal information, its efforts to combat harmful content and its competitive practices. But he's resisted those calls since appearing before Congress last year to address the Cambridge Analytica flap, opting instead to meet privately with officials, including during a series of recent closed door meetings in Washington.

The Facebook CEO addressed the controversy during his July open meeting, telling employees, "It just doesn’t really make sense for me to go to hearings in every single country that wants to have me show up."

But that hasn't stopped U.S. lawmakers from taking issue with Zuckerberg's approach. Senate Commerce Chairman Roger Wicker (R-Miss.), for one, said he was "deeply disappointed" the CEO declined to take part in a September hearing on violent and extremist content online, according to a letter to Zuckerberg obtained by POLITICO. The executive has also taken heat for declining to testify on online disinformation before a coalition of officials from the United Kingdom and Canada, among others.

In the U.S., Warren has been particularly blunt in her critiques of the company. The senator excoriated Facebook in March for briefly taking down several of her campaign ads touting her proposal to break up the company. Facebook and other tech giants have "bulldozed competition, used our private information for profit, and tilted the playing field in their favor," she tweeted after the incident.

Facebook restored the ads after a POLITICO report detailed the takedowns. The company said the video ads violated its advertising policies by displaying the Facebook logo.

One prominent Facebook critic said Zuckerberg's focus on Warren alone is myopic, given the growing scrutiny of the company across the political spectrum.

“Zuckerberg is personalizing what is actually an increasing consensus," said Open Markets fellow Matt Stoller, who has said Facebook and other tech titans have only been able to make billions by abusing their market power, amassing revenue on data gathered by tracking users and on content produced by publishers and other third parties. “He’s kind of unwilling to deal with the fact that there is now an increasingly political consensus that the economic model for Facebook doesn’t work.”

That coalition might even include some staffers at the Facebook, who have poured money into Warren's campaign through individual donations, despite her pledge to break up their employer. Green maintained that trend may reflect a disconnect between Facebook's CEO and some of its rank and file, who may appreciate from working for a pared-down Facebook, he said.

"Most employees don’t sign up looking to be part of a grotesque monopoly; they just want to make things better," said Green. "Many would feel better about their jobs if someone like Elizabeth Warren allowed them to focus on their companies’ assets.”