At the outset of his testimony before the House Financial Services Committee on Wednesday, Facebook CEO Mark Zuckerberg admitted that when Russians used his site to manipulate the 2016 election, he was put on the defensive. For the rest of the day, federal legislators kept him there, asking straightforward questions he repeatedly struggled to answer. For Zuckerberg, even inquires about Facebook’s support of free expression — which he outlined in a speech at Georgetown University last week — proved to be difficult to answer. By the end of the day, it was easy to forget why Zuckerberg was ostensibly there: to talk about his company’s cryptocurrency initiative, Libra. When representatives asked Zuckerberg about Facebook’s policy of allowing politicians to lie in ads, his wavering answers stood out. An intense exchange with Democratic Rep. Alexandria Ocasio-Cortez was telling. “Would I be able to run advertisements on Facebook targeting Republicans in primaries saying that they voted for the Green New Deal? If you’re not fact-checking political advertisements, I’m just trying to understand the bounds there,” Ocasio-Cortez asked. “Congresswoman, I don’t know the answer to that off the top of my head. I think probably,” Zuckerberg replied.

“So you don’t know if I’ll be able to do that?” “I think. Probably.” “Do you see a potential problem here?” replied Ocasio-Cortez.

“Do you see a potential problem here?”

Facebook claims it prohibits speech that leads to voter suppression. But by allowing misinformation that portrays candidates saying things they haven’t, it may suppress the vote anyway, experts told BuzzFeed News.

“The company and Mark do not seem to understand what voter suppression looks like in 2019,” Vanita Gupta, president and CEO of the Leadership Conference on Civil and Human Rights, told BuzzFeed News. “You don’t have to look further than the 2016 election to see how foreign actors used these very same tactics that domestic actors have used for centuries in this country that undermine participation of voters of color.” Judd Legum, who writes the Popular Information newsletter, echoed Gupta’s concerns about Zuckerberg. “He can’t be straightforward, because the policy is inherently inconsistent,” Legum said. “He says Facebook will police voter suppression but not misinformation. But one of the most effective ways to suppress votes is to push misinformation. So the policy doesn’t make sense.”

“So the policy doesn’t make sense.”

Zuckerberg also stumbled in a back-and-forth with Democratic Rep. Sean Casten, who asked him: If a member of the American Nazi Party ran for office, could they purchase an ad that included hate speech otherwise prohibited by Facebook? “I’m asking the question whether you can spread hate speech if you are an elected official, or trying to be an elected official, that you would not be allowed to if you were not in that capacity,” Casten said.

“Congressman, I think that depends on a bunch of specifics that I’m not familiar with this case and can’t answer to,” Zuckerberg replied. “Well, that’s rather shocking,” said Casten.

.@RepCasten asked Mark Zuckerberg if a member of the American Nazi party who is running for office (which was the case last year in Illinois) can speak on @facebook in a different fashion than a member of the Nazi party who is not running for office. Zuckerberg could not answer.

In a marathon day, perhaps Zuckerberg’s worst moment came when he couldn’t keep up with questioning from Democratic Rep. Joyce Beatty.

.@RepBeatty guts Mark Zuckerberg on civil rights and housing advertisements