Some observers, including people inside the Public Broadcasting Service, see these recent developments as troubling. PBS, they say, is being forced to toe a more conservative line in its programming by the Republican-dominated agency that provides about $30 million in federal funds to the Alexandria-based service.

Officials at the agency, the Corporation for Public Broadcasting, say they are merely seeking to ensure balance and fairness in the network's presentation of political news and ideas.

Under its mandate from Congress, which created the agency in 1967, CPB is required to act as an independent buffer between lawmakers and public broadcasters, although it can set broad programming goals. Appointees of President Bush currently control the majority of seats on CPB's eight-member board. Each board member serves a six-year term.

Typically one of the quietest bureaucracies in Washington, the quasi-governmental CPB has been unusually active in recent weeks. CPB this month appointed a pair of veteran journalists to review public TV and radio programming for evidence of bias, the first time in CPB's 38-year history that it has established such positions. PBS officials were unaware that the corporation intended to review its news and public affairs programs, such as "The NewsHour With Jim Lehrer" and "Frontline," until the appointments were publicly announced.

In negotiations with PBS earlier this year, the corporation also insisted, for the first time, on tying new funding to an agreement that would commit the network to strict "objectivity and balance" in each of its programs -- an idea that PBS's general counsel described in an internal memo as amounting to "government encroachment on and supervision of program content, potentially in violation of the First Amendment."

Late last week, CPB's board declined to renew the contract of its chief executive, Kathleen Cox, a veteran administrator at the agency. She was replaced by Ken Ferree, a Republican who had been a top adviser to Michael Powell, the former chairman of the Federal Communications Commission. The Ferree appointment followed the dismissals or departures in recent months of at least three other senior CPB officials, all of whom had Democratic affiliations.

"We don't want to be alarmist, but I would be less than honest if I said there wasn't concern here," said one senior executive at PBS, who insisted on anonymity because CPB provides about 10 percent of its annual budget. "When you put it all together, a pattern starts to emerge."

A senior FCC official, who would not speak for attribution because he must rule on issues affecting public broadcasting, went further, saying CPB "is engaged in a systematic effort not just to sanitize the truth, but to impose a right-wing agenda on PBS. It's almost like a right-wing coup. It appears to be orchestrated."

In an interview yesterday, CPB board chairman Ken Tomlinson called such comments "paranoia," and said critics of CPB's initiatives should "grow up."

"We're only seeking balance," said Tomlinson. "I am concerned about perceptions that not all parts of the political spectrum are reflected on public broadcasting. [But] there are no hidden agendas."

Asked for specific examples of slanted or unfair programming, Tomlinson declined to name any. "You've heard the same complaints of bias that I have in congressional hearings year after year," he said.

In fact, congressional Republicans have been generally critical of public broadcasting's news and informational programming for years, saying it favors liberal ideas. These criticisms fueled a movement led by then-House Speaker Newt Gingrich to "zero out" CPB's federal funding a decade ago. Those efforts failed; federal appropriations to CPB have grown 40 percent since then, to some $386.8 million this year. About 90 percent of this money is passed directly to public radio and TV stations, which then pay fees to PBS and National Public Radio for programming such as "Nova" and "All Things Considered."

However, conservatives were exercised that Moyers -- an outspoken liberal -- was involved in hosting a weekly newsmagazine called "Now." (Moyers left the show in December, citing personal reasons.) PBS responded, in part, by trying to recruit Gingrich to host a weekly program. It wound up developing public affairs shows starring the Wall Street Journal's conservative pundits and Tucker Carlson, a columnist for the conservative Weekly Standard and a co-host of CNN's "Crossfire." (Carlson has since left PBS and CNN for a job at MSNBC.)

In January, PBS came in for more criticism, this time a rebuke from Education Secretary Margaret Spellings over an episode of a children's travelogue program in which a rabbit character named Buster paid a visit to two families headed by lesbians. PBS pulled the episode from distribution to stations around the country.

Tomlinson would not comment on specific programs. He said CPB's efforts were aimed at making "incremental changes that meet the needs of the American people and the aspirations of the American people." Tomlinson, who ran the Voice of America during the Reagan administration and was formerly editor in chief of Reader's Digest, became chairman of CPB in September 2003.

The corporation's own research indicates broad public satisfaction with the quality of news programming on PBS and NPR. A series of focus group sessions and two national surveys conducted by two polling firms -- the Tarrance Group and Lake Snell Perry & Associates -- found few perceptions of bias in PBS's or NPR's reporting in 2002 and 2003. For example, among people who identified themselves as "news and information consumers," 36 percent said PBS's coverage of the Bush administration in 2003 was "fair and balanced," and 46 percent offered no opinion. Eleven percent judged NPR's coverage of the Middle East to be biased, and this group split almost equally between those who felt NPR was biased toward Israel and those who felt it was biased toward the Arab or Palestinian side.

Wayne Godwin, PBS's veteran chief operating officer, said in an interview yesterday that he wanted to give CPB's new chief executive, Ferree, some time before he drew conclusions. "They're in such a significant state of flux at this time that we want to be fair in looking at it," he said.

He added, "I don't know that Ken [Tomlinson] is or is not trying to change our programming. . . . I will say there is reason to remain aware and vigilant to what is going on. The long run will determine if he wants changes."

Tomlinson said his goal is to seek increases in federal funding of public broadcasting in order to strengthen it in an increasingly competitive media environment. "Public TV, public broadcasting, is in trouble," he said. "It will wither and die if we continue the way we have. That's why it's so important for us to rally national support for it. If we don't have true excellence, we won't be able to gain the support we need. We have to make sure that these [programming] concerns don't prevent us from gaining the national consensus we need."