By John D. McKinnon and Ryan Tracy

WASHINGTON -- The chief executives of Facebook Inc. and Twitter Inc. told lawmakers they did better in fending off election interference in 2020, while acknowledging mistakes and signaling an openness to more regulation.

The tough tone of questions from both parties at a congressional hearing Tuesday suggested that social-media giants face higher risks of new regulation in the next Congress that begins in January.

At the Senate Judiciary Committee hearing conducted over more than four hours by videostream, Facebook's Mark Zuckerberg and Twitter's Jack Dorsey touted improvements their companies made in blocking or reducing misleading information in the 2020 election. That led to less interference, the CEOs said. By contrast, the 2016 election was marred by meddling from Russia aimed at helping elect Donald Trump.

"I am proud of the work we have done over the past four years to prevent election interference and support our democracy," Mr. Zuckerberg said in his opening statement. "Millions of Americans used our service to talk about the campaigns, access credible information about voting and register to vote."

The pitch didn't appear to persuade lawmakers, who renewed concerns about the platforms' power and reach as well as their handling of specific election-related content.

Judiciary Chairman Lindsey Graham (R., S.C.) said the companies should prepare for modifications to federal legal protections shielding them from liability for user-posted material. Those protections also give the platforms wide latitude in policing content.

"When you have companies that have the power of governments...something has to give" in the legal shield known as Section 230, Mr. Graham said. "[Section] 230 as it exists today has got to give."

Republicans also complained that the platforms continue to censor conservative speech, a charge that the platforms and Democrats generally reject.

"While we strive to do as well as possible and be as precise as possible, we will make mistakes," Mr. Zuckerberg said after Sen. Mike Lee (R., Utah) read a list of actions taken against content adopting a conservative point of view.

"They may be mistakes, but they are mistakes that rhyme," Mr. Lee said.

Democrats raised their own concerns, including that some of the platforms' current content restrictions could hinder them in a crucial Georgia runoff election in January that likely will decide control of the Senate.

"I'm concerned that both of your companies are in fact backsliding or retrenching" in efforts to combat misleading information in the Georgia race, said Sen. Richard Blumenthal (D., Conn.). He said the hearing points the way to action on tech issues in the next Congress, characterizing the companies' efforts to combat false information "baby steps" and adding, "You must do much more...to meet this moment and put your power and money on the right side of history."

Mr. Zuckerberg touted Facebook's efforts to combat misinformation and voter suppression. He noted that the company partnered with election officials to remove false claims about polling information and put warnings on more than 150 million pieces of content following reviews by third-party fact checkers. The company also attached informational labels to content that sought to undermine the legitimacy of the election, Mr. Zuckerberg said.

Mr. Dorsey told senators that Twitter's new policies for labeling or removing false and misleading information marked a big step forward, even though those measures drew complaints from Mr. Trump after some of his own tweets were labeled misleading. Those tweets addressed mail-in voting, violent protests, the coronavirus and claims that he won the presidential election.

When Sen. Dianne Feinstein (D., Calif.) suggested Twitter had done too little by labeling Mr. Trump's tweets but not taking them down, Mr. Dorsey said the platform is "focused on providing more context to people."

Sen. Ted Cruz (R., Tex.) criticized the labeling practice as turning Twitter into a publisher making editorial decisions. He pointed to one label directing users to a page stating, "Voter fraud of any kind is exceedingly rare in the United States."

"That is taking a disputed policy position, and you are a publisher when you are doing that," he said. "You don't get to pretend you're not a publisher and get a special benefit under Section 230 as a result."

Mr. Dorsey said Twitter's page was "pointing to a broader conversation with tweets from publishers and people all around the country." At another point, he said the company is "learning and improving how we address these challenges and earn the trust of the people who use Twitter."

Election officials have reported no evidence of widespread fraud in the 2020 election and have defended the process as fair.

Both executives signaled cautious support for modifying Section 230 of the Communications Decency Act, which gave online platforms near-total legal immunity for the acts of their users as well as broad powers to police their content.

"It may make sense for there to be liability for some of the content that is on the platform," the Facebook chief said. He said Facebook stands ready "to work with Congress on what regulation could look like, whether that means Section 230 reform or providing guidance to platforms on other issues such as harmful content, privacy, elections and data portability." He called for a requirement that platforms report quarterly on content moderation.

Mr. Dorsey said platforms ought to disclose more about their policies and decisions, including actions taken by algorithms. He encouraged Congress to work with industry to build on Section 230, whether through additions, industry self-regulation or a new legislative framework. He warned against laws that would simply carve out certain types of activity from Section 230's shield, saying that would favor large incumbent companies.

Mr. Graham announced the hearing before the election to "focus on the platforms' censorship and suppression" of disputed articles in the New York Post that made allegations against President-elect Joe Biden, then the Democratic nominee, which his campaign denied. Twitter initially blocked tweets of the articles, including from the Post.

Twitter later said it would allow posts about the articles, which the Post said were based on documents obtained from a laptop owned by Hunter Biden, Mr. Biden's son, and concerned international business dealings, including in China. The Biden campaign disputed the allegations made in the Post articles, which The Wall Street Journal hasn't independently verified.

Sen. John Cornyn (R., Texas), pressed Mr. Dorsey about Twitter's initial response to the Post's content. "You do realize that by taking down that story you probably gave it more prominence and visibility than it ever would have gotten had you left it alone," he said.

"We realize that," Mr. Dorsey said. "And we recognize it as a mistake that we made both in terms of the intention of the policy and also the enforcement action of not allowing people to share it publicly or privately, which is why we corrected it within 24 hours."

Write to John D. McKinnon at john.mckinnon@wsj.com and Ryan Tracy at ryan.tracy@wsj.com

(END) Dow Jones Newswires

11-17-20 1639ET