Facebook CEO Mark Zuckerberg testifies before a joint hearing of the Commerce and Judiciary Committees on Capitol Hill in Washington, Tuesday, April 10, 2018, about the use of Facebook data to target American voters in the 2016 election. (AP Photo/Carolyn Kaster)
Facebook CEO Mark Zuckerberg testifies before a joint hearing of the Commerce and Judiciary Committees on Capitol Hill in Washington, Tuesday, April 10, 2018, about the use of Facebook data to target American voters in the 2016 election. (AP Photo/Carolyn Kaster) Credit: ap photograph

Washington — Facebook chief executive Mark Zuckerberg endured an hours-long grilling by dozens of U.S. senators Tuesday during which he repeatedly apologized and promised privacy reforms but also pointedly defended his company against the threat of new legislation.

Zuckerberg invoked Facebook’s unlikely journey — from a tiny startup he co-founded in his Harvard dorm room 14 years ago to a social media behemoth — in explaining Facebook’s frequent privacy missteps and its failure to spot and defeat Russia’s aggressive campaign to manipulate American voters in 2016 and beyond.

Senators repeatedly challenged Zuckerberg’s explanations in the wide-ranging hearing, a rare joint session before two Senate panels — the Commerce and Judiciary committees — with 42 senators questioning the Facebook executive.

“If Facebook and other online companies will not or cannot fix these privacy invasions, then we will,” said Sen. Bill Nelson, Fla., the highest-ranking Democrat on the Commerce Committee.

But for more than four hours, there was no flash point or loss of composure for Zuckerberg, who was appearing in his first congressional hearing after avoiding such scrutiny for years. His steadiness in the face of tough questioning helped quell the air of crisis that surrounded not just Facebook but also Silicon Valley in general, where collecting user data is essential to many businesses.

Facebook’s stock price, sagging since last month’s revelations about how the political consultancy Cambridge Analytica improperly gained access to personal information on 87 million Facebook users, rose during his testimony to end up 4.5 percent for the day, outperforming a generally strong market.

Still, the issues raised in the hearing strike at deep problems for one of the most highflying technology companies. Gallup found in a poll released this week that 43 percent of Americans are “very concerned” about Facebook’s invasions of privacy — an increase of 13 percentage points since 2011, when Gallup conducted a similar poll.

Zuckerberg, who traded his trademark T-shirt and hoodie for the standard Capitol Hill garb of a dark suit and tie, had holed up with advisers in Washington over the weekend to prepare for the hearing. His tone was one of practiced and patient contrition as he described the company’s recent failings and efforts to remedy them.

“It’s clear now that we didn’t do enough to prevent these tools from being used for harm as well,” Zuckerberg said. “And that goes for fake news, foreign interference in elections and hate speech, as well as developers and data privacy.”

Zuckerberg took responsibility for the missteps. “We didn’t take a broad enough view of our responsibility, and that was a big mistake. And it was my mistake, and I’m sorry. I started Facebook, I run it, and I’m responsible for what happens here.”

Yet there was a broader context to the hearing, coming amid rising complaints about how a range of leading tech companies profit from virtually unfettered access to user data — something increasingly restricted in Europe and elsewhere in the world.

In other comments, Zuckerberg singled out Facebook’s inability to identify and combat Russian disinformation efforts as one of his “biggest regrets” and added, “One of my top priorities in 2018 is getting this right.”

He also confirmed for the second time since February that Facebook officials have been interviewed by investigators for special counsel Robert Mueller, who have been looking into Russia’s role in influencing the 2016 election.

Zuckerberg’s acknowledgments of responsibility punctuated an extraordinary shift in tone for him and the company. He has strained in recent weeks to convince lawmakers, users and regulators that Facebook is determined to deliver meaningful change after repeated privacy controversies.

The House Energy and Commerce Committee has its own hearing scheduled for this morning.