Facebook’s Mark Zuckerberg and Twitter’s Jack Dorsey will face accusations from Republican senators that the companies censor conservative content, after several of President Donald Trump’s social media posts claiming voter fraud were labeled as false or misleading in the wake of the election.

The CEOs of the social networks are scheduled to testify before the Senate Judiciary Committee on Tuesday in their second congressional appearance in a month to defend themselves against charges of silencing conservatives.

The session is likely to focus on Twitter and Facebook’s handling of Trump’s statements about the election process and outcome, many of which have been labeled as false or misleading, as well as their treatment of an October story in the New York Post that was seen as potentially damaging to Democrat Joe Biden.

During a tense hearing that month, Zuckerberg and Dorsey heard complaints that they were trying to tip the scales for Biden in the election ahead. Now they’re facing a GOP that for the most part hasn’t recognized Biden as the president-elect.

The censorship complaints aren’t the CEOs’ only political problem: Many conservative users are trying out a competitor, Parler, that courts right-wing influencers. Some moving to Parler are urging others to follow them there. The social media sites must also watch for hints about what policies will be adopted by President-elect Biden, who has expressed concerns about some of the companies’ practices.

Alleged bias against conservatives has long been Republicans’ greatest charge against social media platforms, but the 2020 U.S. election has brought those accusations to the fore. Addressing reporters at the White House two days after the election, Trump himself made baseless claims of “historic election interference from big media, big money and big tech.”

Trump has been contesting the election loudly and repeatedly on Facebook and Twitter, and is now breaking the companies’ election-related rules on an almost-daily basis.

On Twitter, dozens of Trump’s tweets since election night have been labeled for various rule violations, including sharing misleading information about voting results or trying to diminish election returns. On Sunday, he pulled back from a tacit concession, tweeting that Biden had only won in the eyes of the media.

Facebook, too, has been labeling most of Trump’s posts since the Nov. 3 election, though it labels all political posts regardless of accuracy. Still, some of the recent labels directly contradict statements Trump is making about the outcome, and read: “Joe Biden is the projected winner of the 2020 U.S. Presidential Election.”

These labels are likely to be a topic of discussion at Tuesday’s hearing. Although posted by private companies, many conservatives see them as an infringement on free speech, or at least an effort to diminish the president’s message and limit debate.

Many GOP senators, eager to energize their voters in two Jan. 5 runoffs in Georgia that could hand Senate control to Democrats, have doubled down on Trump’s claims about the election, although they’ve largely focused on the media’s role in calling the race and unsupported claims of voter fraud. These include Senators Lindsey Graham, the Judiciary Committee’s chairman, and Ted Cruz, who sits on the panel.

Some Democrats, meanwhile, would prefer Facebook and Twitter remove Trump’s posts entirely, but both companies have argued that it’s in the greater public interest for people to hear from elected leaders. Zuckerberg has argued that the best way to fight misinformation is with more information—a nod to Facebook’s banners and labels that click through to authoritative election information.

These tensions already played out once in recent weeks, when Zuckerberg and Dorsey testified at the Senate Commerce Committee alongside Google CEO Sundar Pichai. The Facebook and Twitter executives faced sharp questioning over their moves to curb a New York Post story about the international business dealings of Joe Biden’s son. The companies cited questions about the story’s sources.

“Who the hell elected you and put you in charge of what the media are allowed to report and what the American people are allowed to hear?” Cruz, who also sits on that committee, shouted at Dorsey during the October hearing. The Texas Republican has also been posting about the election on Parler, which has seen its downloads skyrocket since the election.

Tuesday’s hearing was initially called to address New York Post story, but the topic has since been broadened to focus on “Censorship, Suppression, and the 2020 Election,” according to the committee. The panel has also announced plans to push forward a Graham bill to rein in the companies’ liability protections for policing content and take away their discretion over removing political posts.

The session could signal how Republicans, who are likely to hold onto the Senate, may seek to target the companies next year, particularly if they continue to anger conservatives. Twitter has confirmed that once Trump leaves office, he won’t receive special treatment on its platform, meaning his repeated policy violations could lead to more severe punishments like account freezes or suspensions.

The companies, meanwhile, are unlikely to have an easier time under the incoming Democratic White House. Biden and his campaign team have criticized Facebook’s handling of Trump’s account and misinformation for months, including since the election. Biden has also been vocal about wanting to revisit the companies’ legal protections from third-party content liability, known as Section 230 of the Communications Decency Act.

Biden is also expected to take a tougher approach to antitrust enforcement than President Barack Obama did. Facebook is poised to face at least one competition lawsuit from the U.S. Federal Trade Commission and a coalition of states in coming weeks, Bloomberg has reported.

—Bloomberg News