When Katie Couric looked into a camera at CBS News headquarters on West 57th Street in New York on Tuesday and said, "Hi everyone," an important, maybe vital institution of American society entered a new phase in its struggle to survive.

		Ed Fouhy is a retired television journalist. He worked as Washington bureau chief for CBS, ABC and NBC.

Ms. Couric, first woman to be solo anchor of the network evening news, is the center of attention. But a bigger question than whether she will be successful is whether the program she anchors and the other two like it will withstand the seismic upheaval in the way Americans get their news.

Network news as a program form is as old as television and has held our attention with remarkable tenacity. The old boys -- Walter Cronkite, David Brinkley, John Chancellor, Frank Reynolds -- held sway for two decades; a new generation came into our living rooms beginning 25 years ago when Dan Rather replaced Mr. Cronkite on CBS, Tom Brokaw followed Mr. Chancellor at NBC and Peter Jennings manned the desk at ABC.

Each had his day on top of the ratings as they visited and sometimes comforted us every night for more than 20 years. Then, one by one they dropped away, Mr. Jennings dead of cancer, Mr. Rather a victim of shoddy reporting, Tom Brokaw retired.

CBS News lifer Bob Schieffer, who kept the chair warm for Ms. Couric, expanded third-place CBS's audience by 800,000 viewers in his brief tenure. Brian Williams, who succeeded Mr. Brokaw at NBC, lost about as many, while Charles Gibson, as comfortable and familiar as an old shoe, stabilized star-crossed ABC News last June just as news audiences took their seasonal dive.

Now the competition begins anew, not just among Mr. Gibson, Ms. Couric and Mr. Williams, but also between their traditional TV program form and the new ways of delivering news that have slowly loosened the networks' once total grip on the nation's serious news viewing habits.

For the last 25 years audiences for the three have slowly eroded, leading Cassandras to predict the end of network news, even the end of the once proud network news organizations with their worldwide resources and authoritative reporters.

But the end has not come and close observers of network television have been slow to join that chorus. Sure, network news audiences have declined, but surprisingly less than the audience that once could be counted on to tune into the networks' other offerings: sitcoms, dramas and headline sports events.

The network evening news programs have outpaced cable upstarts CNN, MSNBC and Fox, whose audiences are small compared to the Big Three, but allow Americans to get news headlines whenever they want them.

Despite high-speed Internet connections in 42 percent of American homes that enable quick news fixes throughout the day, roughly 27 million homes will host network news anchors tonight. A smaller audience, to be sure, than in 1980 when CNN debuted, but still a hefty number.

Like all news organizations, the networks have scrambled to stay up with the digital times. The technically agile can now download ABC and NBC from iTunes; ABC also streams an early edition of World News on its Web site. CBS, the most innovative of the three, allows visitors to assemble their own newscast with video and news reports that reflect their personal interests and taste. But all of the building blocks for these online versions come from the news-gathering effort that mainly supports the evening news.

The shares of the $455 million advertisers spend to reach network news viewers will be at stake as the Gibson-Williams-Couric battle is joined. But far more important will be the future of network news as a journalistic institution.

Aside from the few national daily newspapers with their elite audiences, the networks produce the only countrywide news service that cuts across geography, ideology, income and education levels. They deliver a mostly serious news report to a mass audience that otherwise is chopped into demographic slivers designed to appeal to this or that advertiser.

There is great value in providing serious news for a nation facing terrorists capable of inflicting traumatic damage. Network anchormen (and now one woman) provide the glue that holds a vast nation together at times of crisis, and those times lie ahead as surely as the rising of the tide tomorrow. The anchors can provide viewers with a sense of community, a sense that everyone is in this together, whether the "this" is a terrorist attack, another Katrina or a disputed presidential recount.

The authority of the anchor -- the feeling that he or she represents a news division with hundreds of people capable of swarming over the big story -- cannot be duplicated by any other news-gathering organization.

Cable news with its thin sourcing, often glib but shallow reporting and ideological spin cannot match the voice-of-God authority of network anchors. Web bloggers dish opinions but are short on original reporting.

Sadly, the networks' authority has been affected by flirtations with tabloid fare like the JonBenet Ramsey murder, but most nights their reporting is accurate, objective, occasionally thoughtful.

With 50 years of TV history behind them and a news environment exploding with change around them, network news departments will perform a balancing act again this fall, ferociously competing with one another, while broadening their digital offerings and still honoring a tradition of serious journalism.

They must get the balance right, not only for their own well-being, but because we all have a stake in how successful they are in providing sober, credible, authoritative reporting in times of crisis.