(FORTUNE Magazine) – Leslie Moonves got a little carried away last year talking about the changes he was mulling for the CBS Evening News after the departure of Dan Rather. "On the one hand we could have a newscast like The Big Breakfast in England, where women give news in lingerie," he told the New York Times Magazine. "Or there's Naked News, which is on cable in England. I saw a clip of it. It's a woman giving the news as she's getting undressed. And then, on the other hand, you could have two boring people behind a desk. Our newscast has to be somewhere in between."

Moonves, who then ran the network for Viacom and now is CEO of the new CBS Corp., was clearly trying to be droll, but he was also making a point. The CBS Evening News had been stuck in third place for more than a decade, and Moonves had started publicly plotting a ratings turnaround--not unlike the one that he had pulled off for the network in prime time with hits like CSI and Survivor. He floated the idea of a multi-anchor format similar to CBS's The Early Show. He didn't rule out the notion of someone from the entertainment world--like Jon Stewart, host of Comedy Central's The Daily Show--as the new anchor. Moonves even talked about blowing up the news division, as if that might help matters.

Some of his musings may have been over the top, but all three networks had to rethink their evening news broadcasts. The longtime anchors of CBS, ABC, and NBC were leaving the stage. The audience for evening news at 6:30 had been shrinking for a quarter-century. The median age of viewers was about 60--not a demographic coveted by advertisers. But who else was home watching the news at that time? The network news divisions, it seems, had to take drastic measures: Get younger, prettier, webbier.

There has indeed been plenty of change since then. NBC and ABC now have younger anchors with responsibilities that Rather, Tom Brokaw, and the late Peter Jennings never would have dreamed of when they ascended their thrones nearly 25 years ago. Forty-six-year-old Brian Williams, Brokaw's successor at NBC Nightly News, doesn't just host the newscast. He blogs--contributing to the Nightly News website six times in a single day recently when he had three interviews with President Bush. "It was pretty extraordinary," said NBC News president Steve Capus in a Jan. 27 interview. "He's helped redefine what the anchor role should be."

ABC was even more ambitious. In December it named Elizabeth Vargas, 43, and Bob Woodruff, 44, co-anchors of World News Tonight, with the plan that one of them would always be on the road reporting. In subsequent weeks Vargas and Woodruff also blogged. They anchored a live, 3 P.M. webcast of World News Tonight updated during the rest of the day. They also started a nightly live feed to the West Coast so that viewers there weren't watching old news. "We are revolutionizing the way the evening news is delivered," Jon Banner, executive producer of World News Tonight, said in December when the changes were unveiled.

Then something happened that reminded everyone in the business what news is, why it matters, and why the cosmetic changes executives make in search of audience are always beside the point. On Jan. 29, while traveling with U.S. troops in Iraq, ABC's Woodruff was seriously injured by a roadside bomb. As FORTUNE went to press, Woodruff was recovering, but the extent of his injuries wasn't known. The tragedy served notice that the news is serious business--not show business. News crews often risk their lives pursuing stories, and unlike, say, a CSI episode, these programs are at their best when they aren't trying to be entertaining. Woodruff, a former corporate lawyer fluent in Mandarin, could have done many things with his life. He chose to go searching for news in places like North Korea, Pakistan, and Israel's West Bank, frequently putting himself in harm's way. Iraq, of course, was a regular stop for a newsman trying to live up to Jennings's example. In network news, some things never change.

It's not at all clear the audience for the shows wants much change either. For all the talk about new formats and distribution, the nightly news show getting the most traction with viewers by one important measure is the CBS Evening News, which has made the fewest changes of any of the networks. Instead of having a woman in lingerie read the news, or even hiring a permanent replacement for Rather, Moonves's network turned the program over last March to 68-year-old Bob Schieffer. A veteran Washington correspondent and host of CBS's Face the Nation, Schieffer is patently old school. He doesn't blog. He is as serious as your life. And maybe that's why, since the current season began in September, the number of people watching the CBS Evening News has risen by 161,000 to 7.6 million, according to Nielsen Media Research. NBC, though still solidly in the lead with 9.8 million viewers, has had a decline of 785,000. ABC's total viewers have fallen by 808,000 to 8.6 million. Schieffer "has certainly turned the Evening News around," says Brad Adgate, research director of Horizon Media, a New York City media buyer.

As talented as Schieffer's younger competitors may be, they are still trying to grow into a role that Schieffer inhabits effortlessly. He chats with his correspondents on the air after they deliver their stories, drawing further revelations out of them. When a correspondent says something that Schieffer finds outrageous--for example, reporting that Republicans in Congress were talking about making it easier for the President to spy on U.S. citizens--he lets it show, subtly. "Bob Schieffer is an expert," says Henry Schleiff, CEO of Court TV. "He's paid his dues, and while all the networks are running away from people his age, the audience is embracing him--because he's real."

CBS's competitors minimize the network's gains. They argue that the real reason for the success of the Evening News is the departure of Rather, a lightning rod for conservatives, who accused him and the network of political bias. "A year ago CBS was coming right out of the problems with Memogate, and so if they grow [on top of] that, it's all relative," said Capus, in the interview before Woodruff was injured. "All I'll say is there is a very clear No. 1 broadcast, there is a very clear No. 2, and there's a very clear No. 3. And we're delighted to be leading the way."

The truth is that Schieffer's success raises difficult questions for all three networks. If the only anchor pulling in new viewers at 6:30 P.M. is a 68-year-old, what's the point of hiring younger ones and tweaking the format? As everybody knows by now, CBS is hoping to lure 49-year-old NBC Today Show host Katie Couric to the Evening News. (CBS News president Sean McManus declines to comment on Couric. But Schieffer acknowledges CBS's interest and says he is a "strong advocate" of hiring her. He adds that he's not interested in the permanent anchor position himself.)

Surely CBS would have to at least match her NBC salary-- estimated to be $15 million a year--to lure her away. There's no reason to think she wouldn't do as good a job as any of the other young anchors. There is also talk about adding Couric to the 60 Minutes lineup as part of a deal with the network. But would it make more sense to stick with Schieffer and bank those modest gains? If the competitors' numbers continue to decline at the current rate, CBS would catch up with both ABC and NBC in a few years. It could end up with the superior newscast as well.

That would be a revolutionary strategy. It would mean admitting the painfully obvious, that evening news shows, while still profitable, appear to be in a state of decline similar to that of newspapers and newsmagazines. It's virtually impossible to grow the audience for these shows significantly because they are on at a time when fewer and fewer people are home. And no network is going to run the news at 8 P.M., when they can attract so many more viewers with Survivor.

Maybe all the digital strategies, the blogs and webcasts and podcasts, will work, although it's way too soon to say whether they can generate enough cash to support global newsgathering. If not, ABC, CBS, and NBC should be uniquely qualified to maintain the profitability of their declining assets. After all, they've been losing news viewers for 25 years. It should be a core competency for every network news president by now.

DEVIN LEONARD, a senior writer at FORTUNE, can be reached at dleonard@fortunemail.com.