WASHINGTON — In September, the White House nominated a lawyer to be a commissioner on the Federal Communications Commission. One line on his résumé: aiding the administration’s push to limit an important legal shield for Silicon Valley companies.
That same month, the Justice Department sent Congress a detailed proposal for how to change the law behind that legal shield.
And on Wednesday, lawmakers will confront the chief executives of Facebook, Google and Twitter. The topic of discussion: whether that law enables bad behavior from the companies.
The Trump administration and its allies have fanned out widely in Washington in recent months to attack that law, Section 230 of the Communications Decency Act. The law is considered sacred by social media platforms like Facebook, Google and Twitter, because it protects them from liability for content posted by their users.
Increasingly, the law is criticized by politicians of both parties. Joseph R. Biden Jr., the Democratic nominee for president, has called for it to be revoked, saying it allows the companies to shirk responsibility over what appears on their sites.
But President Trump and Republican lawmakers have been increasingly vocal in the months before Election Day, saying the companies have hid behind the law to suppress conservative views. Their frustration flared up again two weeks ago when Twitter and Facebook limited the distribution of an unsubstantiated New York Post article that was critical of Mr. Biden’s son Hunter.
Their animosity is likely to be on full display at Wednesday’s hearing, when Republicans on the Senate Commerce Committee like Marsha Blackburn of Tennessee and Ted Cruz of Texas are expected to attack the chief executives.
Republicans have invoked the issue as “a cudgel,” said Olivier Sylvain, a law professor at Fordham University who has argued for changes to Section 230. Mr. Trump, he said, is “making a point with his base.”
Judd Deere, a White House spokesman, said the president had been clear about why the issue was important to address.
“He believes the tech monopolies are limiting Americans’ freedom of speech,” Mr. Deere said, “and his administration is taking steps to solve this problem.”
Google, Facebook and Twitter have said in the past that they try to limit the reach of misleading information on their platforms, but that they do not make decisions based on political views. Google declined to comment. Facebook and Twitter pointed to the prepared testimony from their chief executives.
The evidence that conservative speech is subject to unfair treatment online has always been anecdotal. And many conservative personalities, like the commentator Ben Shapiro, have built large audiences on the platforms.
The legal shield, passed in the 1996, has played a key role in the growth of Silicon Valley. It has allowed companies like Facebook and Twitter to expand rapidly without taking on more legal liability with each new post.
The White House’s efforts to weaken the law began in earnest last year when Mr. Trump hosted a Social Media Summit with right-wing influencers, many of whom point to anecdotal evidence to say the platforms have suppressed their views. The attendees included people who had spread conspiracies or doctored content.
In May, Twitter applied fact-checking labels to two tweets by Mr. Trump that made false claims about voter fraud. Days later, the White House announced that Mr. Trump had signed an executive order meant to narrow the protections for the tech companies.
Many lawyers and experts said the president was exceeding his power with the executive order, which ordered the Commerce Department to petition the Federal Communications Commission, an independent agency, to change its interpretation of the law.
In a speech soon after the Commerce Department request, Michael O’Rielly, one of the three Republican commissioners at the F.C.C., seemed to rebuke the request on free-speech grounds.
“It is time to stop allowing purveyors of First Amendment gibberish to claim they support more speech, when their actions make clear that they would actually curtail it through government action,” he said.
At the time, Mr. O’Rielly was awaiting Senate confirmation to a new term at the agency. He said his comments were not a critique of Mr. Trump,
The White House rescinded Mr. O’Rielly’s nomination five days after his speech without an explanation. In his place, it nominated Nathan Simington, a Commerce Department lawyer who helped write the petition that asked the F.C.C. to limit the law. Mr. Trump tweeted in support of Mr. Simington’s nomination.
This month, the commission’s Republican chairman, Ajit Pai, said he would take steps to consider the proposal to limit the law.
“Social media companies have a First Amendment right to free speech,” Mr. Pai said in an Oct. 15 statement. “But they do not have a First Amendment right to a special immunity denied to other media outlets, such as newspapers and broadcasters.”
The White House and its allies have also tried to prod the Federal Trade Commission, which polices the claims that companies make to consumers, to address its concerns with the law.
Mr. Trump’s executive order asked the trade commission to investigate complaints about how social media companies moderate their content, looking at whether they violate the prohibition on “unfair and deceptive” practices. At a hearing in August, Senator Roger Wicker, Republican of Mississippi, asked the agency’s chairman whether it had taken action on the order yet.
The chairman, Joseph J. Simons, pushed back. “Our authority focuses on commercial speech, not political content curation,” he said. Mr. Trump also met with Mr. Simons in recent months to discuss the issue, said a person with knowledge of the meeting, who would speak only anonymously because the person was not authorized to talk publicly about the meeting.
Mr. Trump’s allies on the Senate Commerce Committee are expected to spend the Wednesday hearing asking Mark Zuckerberg of Facebook, Jack Dorsey of Twitter and Sundar Pichai of Google about the companies’ content moderation and use of the legal shield. The Senate Judiciary Committee has also subpoenaed Mr. Dorsey and Mr. Zuckerberg to testify about the way they handle content, in a hearing scheduled for after the election.
Senator Josh Hawley, a Missouri Republican on the Judiciary Committee, said that simply because some conservative personalities were thriving online did not negate instances when conservative content had been taken down. And he disagreed with opponents who say the right is simply trying to work the referees of the information age.
“The point is, there shouldn’t be refs,” Mr. Hawley said.
Many Democrats say the administration’s actions — and those of its allies in Congress — are little more than political theater. Some academic critics of Section 230, too, say the administration’s attacks seem more rooted in politics than a desire for a specific policy outcome.
“There’s simply no reason to have this hearing just prior to the election, except that it may intimidate the platforms, who have shown themselves to be vulnerable to political blunt force in the past,” Senator Brian Schatz, Democrat of Hawaii, wrote in a tweet about the Wednesday hearing.