UPDATE: Nielsen says the TV audience for Monday's debate was 84 million. There were also 17.1 million Twitter interactions related to the debates from 2.7 people in the U.S., according to the audience measurement service.
The previous record for a debate was 80.6 million for the 1980 debate between Ronald Reagan and Jimmy Carter.
That 84 million figure does not include those who watched live streams on YouTube and elsewhere. Not does it include those who watched in such public spaces as bars, airports or student centers.