Through four days, the Democratic convention was seen in an average of 22.5 million households. No other convention - Republican or Democratic - had been seen in as many homes since Nielsen began keeping these records for the Kennedy-Nixon campaign in 1960. There weren't enough television sets in American homes to have possibly beaten this record in years before that.
The convention that comes closest in interest was the 1976 Republican gathering, which averaged 21.9 million homes. That was the year President Gerald Ford fought off a challenge for the nomination from future President Ronald Reagan. For Democrats, the closest came during the 1980 convention where Sen. Edward Kennedy challenged President Jimmy Carter for the nomination.
This year's nomination fight was another epic battle, between Obama and Hillary Rodham Clinton. Even though it was decided before the convention, viewers apparently were drawn to the historic nature of the first black man nominated as a major party presidential candidate.
Nielsen said that 38.4 million people watched Obama's speech as it was carried live by 10 commercial networks: ABC, CBS, NBC, CNN, Fox News Channel, MSNBC, BET, TV One, Univision and Telemundo.
PBS also televised the speech, but didn't pay Nielsen for a count of its national viewership. Based on a sample of several large cities, PBS estimated that an additional 4 million people saw the speech on its network. C-SPAN, which also televised the speech, has no estimate of its audience.
Obama's speech was the fifth-highest-rated, non-sports event watched by blacks in the last 11 years. A 30th anniversary Michael Jackson special on CBS in 2001 was on top.
The acceptance speech was a particular triumph for CNN, which clearly beat the three big broadcasters head-to-head on a news event for the first time ever. An estimated 8.1 million people watched on CNN Thursday.
In general, audience estimates for the convention show the dramatically waning influence of ABC, CBS and NBC in coverage for these events. The three big broadcasters aired only one hour of convention coverage each night, and it seemed a particular handicap on Thursday as its cable competition was able to show the buildup to Obama's speech.
ABC was the second-most network for Obama-watchers, with 6.6 million. NBC had 6.1 million, CBS 4.7 million, Fox News Channel 4.2 million and MSNBC 4.1 million.
The Republican convention begins Monday in St. Paul, Minn.
Republican candidate John McCain sought to take away some of the attention from his rival on Friday by selecting Alaska Gov. Sarah Palin as his running mate.