WASHINGTON (AP) — Less than a week before Election Day, the CEOs of Twitter, Facebook and Google are set to face a grilling by Republican senators who accuse the tech giants of anti-conservative bias. Democrats are trying to expand the discussion to include other issues such as the companies' heavy impact on local news.

The Senate Commerce Committee has summoned Twitter CEO Jack Dorsey, Facebook's Mark Zuckerberg and Google's Sundar Pichai to testify for a hearing Wednesday. The executives have agreed to appear remotely after being threatened with subpoenas.

With the election looming, Republicans led by President Donald Trump have thrown a barrage of grievances at Big Tech's social media platforms, which they accuse without evidence of deliberately suppressing conservative, religious and anti-abortion views.

The chorus of protest rose this month after Facebook and Twitter acted to limit dissemination of an unverified political story from the conservative-leaning New York Post about Democratic presidential nominee Joe Biden, an unprecedented action against a major media outlet. The story, which was not confirmed by other publications, cited unverified emails from Biden's son Hunter that were reportedly disclosed by Trump allies.

Trump, asked by reporters about the companies Tuesday as he left Washington for the campaign trail, said they are trying to suppress revelations of Joe Biden's "corruption."

"They don't want to show corruption, like you have with Biden. That's totally corruption, and everybody knows it," Trump said. "It's very unfair. Nobody has ever seen anything like this. It's not freedom of the press, it's the opposite."

Social media giants are also under heavy scrutiny for their efforts to police misinformation about the election. Twitter and Facebook have slapped a misinformation label on content from the president, who has around 80 million followers. Trump has raised the prospect, without evidence, of mass fraud in the vote-by-mail process.

Starting Tuesday, Facebook is not accepting any new political advertising. Previously booked political ads will be able to run until the polls close next Tuesday, when all political advertising will temporarily be banned. Google, which owns YouTube, also is halting political ads after the polls close. Twitter banned all political ads last year.

Beyond questioning the CEOs, senators will examine proposals to revise long-held legal protections for online speech, an immunity that critics in both parties say enables the companies to abdicate their responsibility to impartially moderate content.

The tech platforms are gateways to news online. Critics say their dominant position in the advertising market has crushed the struggling U.S. news industry, especially local news publishers.

A report issued Tuesday by the committee's Democratic staff cited the additional devastating impact of the recession triggered by the coronavirus pandemic. About 7,000 newspaper employees are expected to be laid off this year, and newspaper revenues will be down 70% from two decades ago, according to the report.

"Local news is an incredible engine for the creation of accurate information. We don't want to lose that infrastructure," Sen. Maria Cantwell of Washington state, the panel's top Democrat, said in an interview.

The Democrats' report accuses the big platforms of unfairly using news content, taking news consumers' data and diverting customers from local news websites, with little compensation. It proposes that Congress enact rules preventing tech platforms from taking local news content without fair payment.

"These unfair and abusive practices should be called out," Cantwell said.

Democrats have focused their criticism of social media mainly on hate speech, misinformation and other content that can incite violence or keep people from voting. They have criticized Big Tech CEOs for failing to police content, homing in on the platforms' role in hate crimes and the rise of white nationalism in the U.S.

Facebook, Twitter and YouTube have scrambled to stem the tide of material that incites violence and spreads lies and baseless conspiracy theories.

The companies reject accusations of bias but have wrestled with how strongly they should intervene. They have often gone out of their way not to appear biased against conservative views — a posture that some say effectively tilts them toward those viewpoints. The effort has been especially strained for Facebook, which was caught off-guard in 2016, when it was used as a conduit by Russian agents to spread misinformation benefiting Trump's presidential campaign.

The Trump administration's Justice Department has asked Congress to strip some of the bedrock protections that have generally shielded the tech companies from legal responsibility for what people post on their platforms.

Trump signed an executive orde r this year challenging the protections from lawsuits under a 1996 telecommunications law. A provision known as Section 230 has served as the foundation for unfettered speech on the internet.

"For too long, social media platforms have hidden behind Section 230 protections to censor content that deviates from their beliefs," Sen. Roger Wicker, R-Miss., the committee chairman, said recently.

The head of the Federal Communications Commission, an independent agency, recently announced plans to reexamine the legal protections, potentially putting meat on the bones of Trump's order by opening the way to new rules. The move by FCC Chairman Ajit Pai, a Trump appointee, marked an about-face from the agency's previous position.

The unwelcome attention to the three companies piles onto the anxieties in the tech industry, which also faces scrutiny from the Justice Department, federal regulators, Congress and state attorneys general around the country.

Last week, the Justice Department sued Google for abusing its dominance in online search and advertising — the government's most significant attempt to protect competition since its groundbreaking case against Microsoft more than 20 years ago.

With antitrust in the spotlight, Facebook, Apple and Amazon also are under investigation at the Justice Department and the Federal Trade Commission.

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Associated Press Writer Kevin Freking contributed to this report.

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