Viewers gathered around the TV in high numbers for Ford-Kavanaugh hearing

Detailed viewership data will be available later on Friday. But the so-called "overnight" ratings showed a dramatic spike in viewership at 10 a.m. ET. Thursday, right when Ford's testimony began.

Interest remained high all day long, with a notable increase in the late afternoon and early evening hours when Kavanaugh defended himself amid questioning by Democratic senators.

The Senate hearing was shown live on the NBC, ABC and CBS broadcast networks along with most cable news channels.

Nearly 20% of US households with televisions were watching the hearings at any given time between 10 a.m. and 6:45 p.m., according to preliminary Nielsen ratings.

That percentage is an average, which means an even greater number of homes watched some part of the proceedings.

The Nielsen data only includes viewership via traditional TV. An untold number of others tuned in to the testimony through radio and streaming video, and at public viewing events.

CBS News said that Thursday was the No. 1 day of the year for its digital channel, CBSN, in terms of live streams. And CNN said that Thursday was its biggest day of 2018 for digital video with 8 million plus live starts on its website and apps -- and more than 10 million including YouTube and Facebook streaming.

It amounted to CNN's biggest live video day since the Trump inauguration, according to a network spokeswoman.

There is no precise way to compare Thursday's viewership to the three days of hearings involving Clarence Thomas and Anita Hill in 1991 because there was only one cable news channel back then, and no internet.

But reporters across the country described scenes reminiscent of 1991: People gathering around TV's in public places and catching parts of the hearings at work, at restaurants, and in airports.