At issue: Section 230 of the Communications Decency Act - which protects companies from liability over content posted by users .

Twitter's Jack Dorsey and Google's Sundar Pichai said the law is crucial to free expression on the internet.

DORSEY: "Section 230 is the most important law protecting internet speech."

PICHAI: "Of course, our ability to provide access to a wide range of information is only possible because of existing legal frameworks like Section 230."

The topic of reforming the law has split U.S. lawmakers - with Republicans and Democrats divided on ways to hold Big Tech accountable for how they moderate content on their platforms and shape political discourse.

SUNDAR PICHAI: "Let me be clear. We approach our work without political bias. Full stop."

Facebook's Mark Zuckerberg said his platform was trying to find a happy medium:

ZUCKERBERG: Democrats often say we don't remove enough content, and Republicans often say we remove too much. [FLASH] And the fact that both sides criticize us doesn't mean we're getting this right. But it does mean there are real disagreements to where the limit of online speech should be."

Republicans on the panel went after Twitter CEO Jack Dorsey for clamping down on President Trump's tweets, especially about mail in voting, labeling them misinformation.

SENATOR ROGER WICKER: "Mr. Dorsey, how does a claim by Chinese Communists that the U.S. military is to blame for Covid remain up for two months without a fact check, and the president's tweet about the security of mail-in ballots get labeled instantly?"

DORSEY: "As we think about enforcement, we consider severity of potential offline harm. And we act as quickly as we can. [FLASH] We saw the confusion it might encourage and we labeled it accordingly."

TED CRUZ: "Who the hell elected you?"

Senator Ted Cruz railed against Dorsey for restricting a New York Post article about Hunter Biden.

CRUZ: "Why Twitter make the decision to censor the New York Post..."

DORSEY: "We had a hacked material policy..."

"When was that policy adopted?"

"In 2018, I believe."

"Go ahead, what was the policy."

"The policy was around limiting the spread of materials that are hacked. We didn't want Twitter to be a distributor for hacked materials."

Democrats raised concerns about the spread of misinformation and extremism on the platforms.

Senator Amy Klobuchar called Facebook's habit of boosting divisive content corrosive:

"The way I look at it, more divisiveness, more time on the platform, more time on the platform, the company makes more money. Does that bother you? What it's done to our politics?"

ZUCKERBERG: "Senator, I respectfully disagree with that characterization of how the systems work."

The hearing itself was questioned -- Democratic Senator Brian Schatz called Wednesday's panel, just days before an election, nothing more than partisan theater.

SCHATZ: "What we are seeing today is an attempt to bully the CEOs of private companies into carrying out a hit job on a presidential candidate."