The questions left unanswered by Facebook, Google and Twitter

Witnesses for Facebook, Twitter and Google arrive at Tuesday's hearing. Photo: Andrew Harnik / AP

The top lawyers for Google, Twitter and Facebook spent more than two hours yesterday explaining how they are cracking down on malicious activity by foreign actors, but we walked away from the hearing with a few unanswered questions. The tech execs will have two more interrogations today by both the House and Senate Intelligence Committees.

What was the overall influence of this Russian campaign? This question is at the heart of the investigation into social media's impact on the election, and it was posed by Hawaii's Sen. Mazie Hirono. But Facebook's general counsel Colin Stretch said he wasn't able to make judgements on voters' motivations last November.