A top priority for the next president of ABC News won't just be figuring out who should one day succeed Diane Sawyer as the anchor of "World News Tonight." It also may be deciding whether there will be an audience worth broadcasting to at all.

With ratings and revenues declining and their core audience growing old, the news divisions of the broadcast networks — like the newspaper and radio industries — are struggling to reinvent themselves for the digital age. The playing field between traditional media and new media has been leveled, but the aftershocks are still being felt.

"Clearly, the journalism business is in a state of overcapacity," said Andrew Tyndall, an industry consultant. "There are a lot of legacy brands that are going to have to shrink. … This is not just the tribulations of ABC News or broadcast television, this is journalism and the transformation the Internet has wrought."

That transformation has been particularly painful at ABC News. David Westin, who said Monday he was stepping down as president of ABC News at the end of the year after 13 years, spent much of his tenure cutting budgets. In April, ABC News wrapped up a brutal round of cuts that saw about 400 people either take buyouts or get laid off. It currently has about 1,000 staffers, which is on par with its rival news divisions at NBC and CBS.

In the spring, Westin said in a staff memo that "now it is time to look to the future." What he didn't say, but apparently was already thinking, was that the future of ABC News would not include him. In his e-mail Monday, Westin indicated he had approached his bosses — Walt Disney Co. chief executive Robert Iger and Anne Sweeney, president of the Disney/ABC Television Group — last month to say it was time for him to go.

Though Westin's exit was apparently voluntary, he had grown weary of constantly finding new ways to cut costs and his ever-strained relationships with Sweeney and Iger, people within ABC News said. Sweeney declined a request for an interview via an ABC spokesman, and a Walt Disney Co. spokeswoman did not return a call seeking comment. Westin did not comment beyond his e-mail.

Although the spotlight is on ABC, all of the broadcast networks are in the same boat. Ten years ago, the evening newscasts of ABC, CBS and NBC averaged 27.6 million viewers, according to Nielsen. Today the three newscasts are averaging 21.8 million viewers, a 21 percent decline.

From a competitive standpoint, ABC has been holding its own against NBC News, which is in first place both in the morning with "Today" and in the evening with "Nightly News With Brian Williams."

CBS is mired in third place both in the morning with "The Early Show" and in the evening with its Katie Couric-anchored newscast. NBC News and ABC News are both profitable, people close to those networks say. Sean McManus, the president of CBS News, recently told the industry magazine Broadcasting & Cable that he was not certain whether his news unit would be profitable this year.

The network news audience also is aging. That means young people are not growing up with the viewing habits of their parents. The networks must groom a new audience if they are to survive. This is particularly true for the three evening newscasts, which all start at 6:30 p.m., a time when many Americans are either still working or commuting home.

The networks also may have to rethink their priorities. All three networks have closed bureaus around the world and slashed production budgets, but they still spend heavily on talent even though there is little evidence that having a high-priced anchor translates into bigger ratings.

"What the networks have to do is spend more on reporters and producers and less on anchors," said Christopher Harper, a former correspondent and producer for ABC News who teaches journalism.