Facebook CEO Mark Zuckerberg remained calm under pressure during five hours of questioning by U.S. senators about a series of recent crises culminating with the latest involving Cambridge Analytica, a political consulting firm that gained access to data about up to 87 million Facebook users.
Overall, Zuckerberg appeared to win the day by avoiding any major stumbles and appearing open to the idea of limited privacy regulation. For their part, the senators were generally gentler with Zuckerberg than expected during the hearing, which risked being a dramatic grilling broadcast live to millions of people at home.
Zuckerberg, wearing a suit and tie instead of his signature grey t-shirt, and looking somber throughout, responded to lawmakers without becoming flustered. He readily apologized for the privacy dust up, saying “It was my mistake. I’m sorry,” and that Facebook had failed to take a “broad enough view” of the possible misuse of its service and developer tools by bad actors.
Much of what Zuckerberg reiterated was what he and his lieutenants have been explaining for the past couple weeks of intense criticism and a falling stock price. But saying it on a national stage, under scrutiny of lawmakers, raised the stakes for the CEO, who had never previously given testimony in Congress.
Zuckerberg’s performance stood in sharp contrast to some public appearances earlier in his career, during which he stumbled with answers while perspiration glistened on his forehead. Since then, he’s grown more polished on stage and able to respond at length to questions as if he’s gone through a crash course in public speaking.
When Zuckerberg didn’t know the answer—and that was often—he told senators that his staff would provide more details later. It had the effect of diffusing some more detailed questions that could have opened Facebook to further scrutiny.
Several times during Tuesday’s hearing, Zuckerberg explained that an academic, Aleksandr Kogan, had misled Facebook about his true intentions in creating a personality quiz app on the social network that harvested user data. Kogan then sold that data to Cambridge Analytica, in violation of Facebook policies.
A few years ago, Facebook changed its terms of its service so that developers could no longer access as much data as before. But for many critics, it was too little, too late.
During the hearing, Zuckerberg directed blame away from Facebook to Cambridge Analytica, saying that his employees had been duped. Indeed, several senators questioning Zuckerberg seemed to take his side and expressed more anger at Cambridge Analytica than Facebook, which had such lax data sharing policies that it’s developer platform essentially operated on an honor system.
A few questions caught Zuckerberg off guard, including one by Sen. Maria Cantwell of Washington, who asked him if data analytics company Palantir scraped Facebook user data to allegedly aid Cambridge Analytica. Zuckerberg seem flustered by Cantwell bringing up Palantir, whose co-founder Peter Thiel is a Facebook board member, and responded, “I’m really not that familiar with what Palantir does.”
Ultimately, Zuckerberg apologized repeatedly for failing to foresee the Cambridge Analytica scandal, and promised that his company is working to prevent similar problems.
Investors appeared to be pleased with Zuckerberg’s performance on Capitol Hill after sending its shares down 15% over the past few weeks for its missteps. On Tuesday, the company’s shares rose 4.5% to $165.04.
Zuckerberg helped his case by reassuring senators that he’s willing to work with them on relatively low-impact legislation that would regulate how online companies handle user data and privacy. Tech companies are notorious for their opposition to regulation, but a small dose would give the industry cover while letting it avoid harsher oversight. Facebook has friends in several Republican senators, who repeated their party mantra that too much regulation would hamstring the next Facebook.
Get Data Sheet, Fortune’s technology newsletter.
If anything concrete comes out of Tuesday’s hearing, it may be that Facebook trims its terms of service, which a number of senators complained is too long and confusing. Zuckerberg replied that Facebook tries “to be exhaustive in the legal documents,” but that the company doesn’t “expect that most people want to read a full legal document.”
On Wednesday, Zuckerberg has another appointment with a House committee, where he will likely answer many of the same questions. If Tuesday was any guide, he’ll be able to avoid any major blows unless the representatives come armed with sharper questions and demand answers from him instead of his staff.