Barack Obama accepted the Democratic nomination for president on Thursday as an estimated 38 million viewers watched on television, setting a new record for convention viewership, according to Nielsen Media Research.

Mr. Obama’s speech — a historic one given his status as the first African American nominee of a major political party — reached significantly more viewers than the comparable addresses in 2004. Coverage of John Kerry’s acceptance speech in 2004 had 24.4 million viewers; coverage of George W. Bush’s convention speech that same year drew 27.5 million.

The audience estimate of 38.3 million means that Mr. Obama’s speech reached more viewers than the Olympics opening ceremony in Beijing, the final “American Idol” or the Academy Awards this year, the Associated Press notes.

Furthermore, the four-night Democratic convention ranks as the most-watched convention of either party, Democratic or Republican, since Nielsen began measuring conventions in 1960.

The four nights of “common coverage” by networks — 10 to 11 p.m. Monday through Thursday — were viewed by an average of 22.4 million households, Nielsen said Friday. Previously, the highest-rated Democratic convention occurred in 1980 with 20.5 million households watching, and the highest-rated Republican convention occurred in 1976 with 21.9 million households watching.

Comparisons to previous conventions must include a number of important caveats. For one thing, until the 1980s conventions were shown on just three networks, and they were covered in greater length than they are now. This year’s conventions are being shown on at least ten TV channels. Additionally, consumers have the option to record the convention and play it back later using a digital video recorder, and those viewers won’t be counted for weeks. Perhaps most significantly, this convention is being streamed online on a number of different Web sites, and the Internet audience will be hard, if not impossible, to measure.

By any measurement, this convention was a popular one among viewers. Early ratings from Nielsen — subject to revision later in the day — suggested that CNN had reached a milestone on Thursday, with more than 8 million viewers during the 10 p.m. hour, more than any of the broadcast networks. If confirmed by Nielsen this afternoon, the ratings would represent CNN’s first time topping the broadcast networks. (Fox News Channel defeated the broadcasters during the Republican convention in 2004.)

The 38 million figure from Nielsen includes the audience on ten networks: ABC, CBS, NBC, CNN, FOX News Channel, MSNBC, BET, TV One, Univision and Telemundo. It does not include PBS or C-SPAN, which also carried the address live. PBS estimated that it averaged 3.5 million viewers between 8 and 11 p.m.