Since the war started, viewership is actually down for ABC's World News Tonight and the CBS Evening News compared to their season averages, according to Nielsen Media Research. NBC's Nightly News is up 3 percent.
During the same period, the average audience for Fox News Channel, CNN and MSNBC combined for any minute of the day has jumped from just under 2 million to 7.4 million.
"There's absolutely no doubt that cable news is where most people are getting most of their information about this," said Erik Sorenson, MSNBC president.
News executives are intrigued by the numbers, wondering if it portends a change for TV viewers or if it is peculiar to the war. During most big events, such as the days following the Sept. 11 terrorist attacks, it has been the evening news broadcasts that have seen spikes in viewership.
Broadcasters say the advantage of the traditional evening news shows is that they take the day's events and put them into perspective in ways the cable networks frequently can't.
But in a story that changes minute-by-minute, that's less of an edge, said David Poltrack, chief researcher for CBS News.
"More than other news stories, you had to find a news source that was constantly updating you," he said, "and that's where the 24-hour news networks had a considerable advantage."
"You don't have to wait for your news," said Teya Ryan, general manager of CNN/US. "To some degree, this is a war being fought in front of us in real time and you don't want to wait until 6:30 or 7 o'clock to get the news. It's happening now and I think people are compelled by that."
For most people, the war is not an all-consuming event, said Paul Slavin, executive producer of World News Tonight. People want to know the latest news, how the U.S. troops are doing and whether Baghdad has fallen.
"The cable networks took this single subject and ran it wall-to-wall," Slavin said. "It was very easy to go to cable any time of the day and find that out."
Reporters embedded with the military also played to cable's strength, he said.
"You would tune in and never know what you were going to get, but that it was going to be fresh and exciting," Slavin said. "You may not have known what was going on, but it was fresh and exciting."
The CBS Evening News audience of just under 7.5 million since the war started is a 15 percent drop. The ABC World News Tonight audience of 9.9 million is down 6 percent. ABC pointed out that the first two days of the war were not included in its ratings because the news aired without commercials; Nielsen doesn't normally count shows without commercials.
NBC, however, rose to 11.4 million.
The broadcast executives point out that their combined audience — just under 29 million people — dwarfs that of the cable networks, but that's only for their half-hour periods.
NBC News President Neal Shapiro suggested that Nightly News bucked the trend because, with MSNBC, NBC News reporters had additional opportunities for exposure. ABC and CBS don't have cable news outlets.
"Our audience can flow back and forth between the networks and our material can flow back and forth," Shapiro said.
The broadcast executives also predicted that, as the war news slows, the cable ratings will recede and the story will begin to play to the strengths of the evening news.
By David Bauder