By John D. McKinnon and Ryan Tracy

WASHINGTON -- CEOs of two big social-media platforms said their companies did better in fending off election interference in 2020, but they still took hits from all political sides at a postelection congressional hearing.

The tough tone of the hearing Tuesday suggested that tech companies continue to face higher risks of new regulation in the next Congress that begins in January.

At the Senate Judiciary Committee hearing conducted via videostream, Facebook Inc.'s Mark Zuckerberg and Twitter Inc.'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.

"Securing the integrity of elections is an ongoing challenge for platforms, and we are committed to continuing to improve our systems, but 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."

But lawmakers renewed concerns from other recent hearings, where they have complained about the platforms' power and reach, as well as how they are handling specific election-related content.

Judiciary Chairman Lindsey Graham (R., S.C.) said the companies should prepare for modifications to their cherished federal legal protections, suggesting that the companies have grown so large and powerful that they no longer need the special legal shield.

"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.

Democrats raised their own partisan concerns, including worries 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 their efforts to combat misleading information in the run-up to the Georgia runoff, said Sen. Richard Blumenthal (D., Conn.).

Mr. Blumenthal also said the hearing points the way to action on tech issues in the next Congress. While praising what he termed "baby steps" by the platforms toward controlling misinformation and other ills in the run-up to the November election, he added, "You must do much more...You need to meet this moment and put your power and money on the right side of history."

Mr. Zuckerberg touted the success of Facebook's extensive efforts to combat misinformation and voter suppression. He noted that the company partnered with election officials to remove false claims about polling information, and displayed warnings on more than 150 million pieces of content after review 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 President Trump after some of his own tweets were hit with labels. Mr. Trump's labeled tweets addressed mail-in voting, violent protests and the coronavirus.

Mr. Dorsey also noted that about 300,000 tweets have been labeled for content that was disputed and potentially misleading.

"We want to be very clear that we do not see our job in this space as done," Mr. Dorsey said in his testimony. "Our work here continues and our teams are learning and improving how we address these challenges and earn the trust of the people who use Twitter."

Both men also signaled cautious support for measures to modify some of the legal protections that social-media platforms currently enjoy under a federal law dating from the mid-1990s. Section 230 of the Communications Decency Act conveyed near-complete legal immunity to the platforms for the acts of their users, and broad powers to police their content. In the wake of growing dissatisfaction with big platforms, lawmakers in both parties have begun considering changes to Section 230.

Mr. Zuckerberg said he would welcome more guidance from government on how to handle content. He also called for a regulatory scheme that would require platforms to report quarterly on their content moderation. 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."

"It may make sense for there to be liability for some of the content that is on the platform," Mr. Zuckerberg said. But he added he didn't think that regulation should mirror rules of the road for news or telecommunications firms, saying tech companies are different.

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 articles in the New York Post that raised allegations against President-elect Joe Biden, which the Biden camp denied. Twitter initially blocked tweets of the articles, including from the Post.

Twitter later said it would allow posts about the disputed Post articles, which the Post said were based on documents obtained from the laptop of Hunter Biden, Mr. Biden's son, and concerned international business dealings, including in China. The Biden campaign has disputed the allegations.

The hearing also will "provide a valuable opportunity to review the companies' handling of the 2020 election," Mr. Graham's announcement said.

The Jan. 5 runoff election in Georgia will decide two Senate seats and will likely determine which party controls the chamber after Mr. Biden is sworn in.

In one runoff, Republican Sen. David Perdue is facing Democrat Jon Ossoff, a documentary filmmaker. In the other, Democrat Raphael Warnock, pastor of Ebenezer Baptist Church in Atlanta, is challenging Republican Sen. Kelly Loeffler.

Democrats are expected to bring up other concerns at the hearing. Sen. Chris Coons (D., Del.), a member of the judiciary panel, wrote a letter to Mr. Zuckerberg Monday accusing Facebook of not doing enough to protect Muslims, citing a Facebook-commissioned civil rights audit that reported in July some Muslims feel "under siege" because of popular content demonizing them. Facebook has noted that the audit described progress as well as shortcomings.

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 1259ET