LOS ANGELES (AP) — President Barack Obama's re-election was well watched but wasn't the TV ratings record-breaker his first victory four years proved to be.

An estimated 66.8 million viewers watched election returns on broadcast and cable networks Tuesday, the Nielsen Co. said Wednesday.

The audience fell short of the record 71.5 million viewers who tuned in to the outcome of the 2008 contest and the historic election of the first African-American president.

NBC came out on top among all networks, averaging 12.1 million viewers during the three hours of prime time, 8-11 p.m. Fox News Channel held the No. 2 slot with 11.45 million viewers, the biggest average ever in the network's 16-year history.

Among other networks, ABC drew 10.52 million viewers, CNN had 9.25 million, CBS had 7.92 million, FOX (broadcast sister to Fox News) had 4.93 million and MSNBC had 4.7 million.

Cable rivals CNN and Fox News both could claim bragging rights, depending on how the pie is sliced.

Networks didn't call the race for Obama until after 11 p.m., so limiting ratings to prime time is akin to measuring viewership for the first three-quarters of an exciting football game decided in the fourth quarter.

Expand the window out to between 7 p.m. and 12 a.m., and Fox News had 10.6 million viewers to CNN's 8.9 million, Nielsen said.

Open it even wider, from 7 p.m. to 2 a.m., and CNN has a narrow edge over Fox News: 8.8 million to 8.7 million. The later hours include Romney's concession speech and Obama's victory speech — events that, presumably, wouldn't appeal as much to the Republicans who make up the bulk of Fox News' audience.

Nielsen measured viewership on 13 networks, including ABC, CBS, FOX, NBC, PBS, Univision, Telemundo, CNBC, CNN, Fox News Channel, MSNBC, Current TV and TV One.