To its conservative critics, public broadcasting is the little liberal idea that won't go away. First Richard Nixon in the early 1970s, then Ronald Reagan in the early '80s, then Newt Gingrich a decade ago tried to reduce substantially or eliminate federal funding of public broadcasting. All three failed.

So the recent tempest over the issue -- Republican-led allegations of biased news reporting, halting efforts to cut federal funds, etc. -- may look to veteran broadcasters like a rerun of a rerun of a rerun. Considering that the federal government got into subsidizing Big Bird and "Masterpiece Theatre" only 38 years ago, public broadcasting has traveled a much-potholed road in Washington.

What is it about National Public Radio, the Public Broadcasting Service et al. that so irks conservatives now? The answer seems to be twofold, reflecting both a general ideological aversion (using taxpayer money to support radio and TV shows) and a specific set of complaints about the alleged leftward tilt of programs hosted by the likes of Bill Moyers and Tavis Smiley.

Just ask Paul Gigot, the conservative editorial page editor of the Wall Street Journal, who was until recently a regular commentator on PBS's stolid "NewsHour With Jim Lehrer." Gigot charges that a "center-left" perspective pervades public broadcasting's ostensibly nonpartisan news discussion programs.

"I haven't done a study of this, but over the years, my perception is that 'Frontline' has" taken this viewpoint, says Gigot. "The conventional wisdom of the reporters on 'Washington Week' is center-left. [PBS talk-show host] Tavis Smiley is a center-left figure, too."

State and local government support of noncommercial broadcasting has its roots in the 1920s, at the start of the radio industry. But the practice reached its official flowering in Washington in 1967, when President Lyndon Johnson signed the Public Broadcasting Act to foster the development of "educational radio and TV," as it was then known. That year, Congress chartered the Corporation for Public Broadcasting and gave it $5 million to hand out to public radio and TV stations. This year, the federal contribution is $387 million, or approximately 15 percent of all the money raised by public broadcasters.

Although the broadcasters say they depend on Washington's help to pay their bills (and to survive, in the case of smaller, rural stations), some critics have never reconciled themselves to the idea of paying for public radio and TV programs -- of any ideological stripe -- with government money.

Supporting opera telecasts or "Mister Rogers' Neighborhood" might have made sense in a three-network world, they say, but not in a 500-channel one that creates plenty of shows equivalent to those once available only on "educational TV" -- children's programs like "Sesame Street," entertainment fare like "Antiques Roadshow," the high-minded documentaries of "Frontline" and "Nova," and news and public-affairs shows like "NewsHour" and "Washington Week."

At a time of massive government budget deficits, amid tight spending on social programs of all kinds, some Republicans assert that Washington's support of public broadcasting is expendable.

"Not that I dislike public television," said Rep. Ralph Regula (R-Ohio), the chairman of the House subcommittee that subsidizes public broadcasting, after the House voted last month to cut some public broadcasting funds. But, he added, "we have limited amounts of money."

What's more, conservatives like to say, those federal funds are subsidizing a system that disproportionately serves the tastes and interests of relatively affluent audiences. "With the obvious exception of 'Sesame Street,' the target audience for PBS isn't remotely poor. It's the well-to-do," conservative commentator Jonah Goldberg wrote in a column this month. "Yes, some poor folks enjoy symphonies and entire shows dedicated to shiitake mushrooms and fennel. . . . But, come on, who're we kidding?"

This may be true of some PBS programs -- Joe Six-Pack isn't likely to TiVo the latest British costume drama -- but not all. In testimony before the Senate last week, PBS President Pat Mitchell noted that its programs draw a weekly audience of some 70 million people. This viewership looks a lot like the nation as a whole, according to Nielsen Media Research.

For example, about 27 percent of PBS viewers graduated from college, compared with 27.6 percent for the U.S. population. Among households that watch PBS, 32 percent earn more than $60,000 a year, compared with 37 percent across the nation. (PBS likes to tell potential sponsors, however, that "public TV members" -- people who gave money to their local station during pledge drives -- are a far more upscale group than PBS viewers as a whole.)

By contrast, NPR's listeners are the relatively more elite kind. The Washington-based service brags in a fact sheet that the 26 million listeners in its combined weekly audience "are distinguished by their high levels of education, professional success and commitment to their communities. They are decision makers, choice consumers and influential leaders." NPR says the mean household income of its listeners is $83,989, or 30 percent above the national average, and that 58 percent of its audience hold a college or graduate degree, which is more than twice the national average.

Indeed, education, not political orientation, "is the variable that defines whether you listen to public radio," says Michael McCauley, an associate professor at the University of Maine who wrote the just-published "NPR: The Trials and Triumphs of National Public Radio."

"There is an elite socioeconomic aspect" to NPR listeners, he says, "but it's not that simple. NPR listeners are more concerned about the world and about policy than the average person. . . . The dirty little secret is that country club Republicans also love NPR."

Nevertheless, the relative affluence of NPR listeners prompts David Boaz, vice president of the libertarian Cato Institute in Washington, to call federal appropriations for public broadcasters "a giant income transfer upward [with] the middle class taxed to pay for news and entertainment for the upper middle class."

None of this gets to the heart of conservatives' ever-present suspicion that public broadcasters favor a liberal worldview. Kenneth Y. Tomlinson, the CPB's chairman, has waged a mini-crusade on this issue in recent months, attacking in particular PBS icon Moyers, a liberal commentator and newsman who until December hosted the newsmagazine program "Now With Bill Moyers" (Moyers is now host of another PBS show called "Wide Angle").

Tomlinson was so unhappy with PBS's perceived left-wing slant that he pushed CPB to fund, and PBS to distribute, two conservative-oriented programs, "The Journal Editorial Report," starring Gigot, and "Tucker Carlson: Unfiltered." (Carlson has since defected to the cable news channel MSNBC.)

To be sure, much of the programming on PBS is of a non-ideological variety. From its headquarters in Alexandria, PBS commissions, finances and distributes about 3,000 hours of programming a year. About a third of this is children's programming; another third is historical, dramatic or cultural in nature, with the balance news and current affairs. Mitchell noted last week that no more than about 30 hours of this programming, or about 1 percent, rose to any level of controversy last season.

PBS's most popular show during the 2004-05 season was the collectibles-appraisal series "Antiques Roadshow," which averaged 5.27 million viewers a week (a level that would probably invite a quick cancellation on a commercial broadcast network). The rest of the top five: documentaries on the boxer Jack Johnson (4.2 million viewers), the Krakatoa volcano (3.85 million), and Broadway musicals (3.7 million); and "Christmas With the Mormon Tabernacle Choir" (3.56 million).

While politics has gotten more attention, PBS's biggest problem may be its demographic trends. While its overall audience has gradually shrunk, as have other networks' in the ever-expanding TV universe, PBS has tended to appeal to really young viewers (ages 1 to 7) and older (those over 50), with a dwindling number of viewers in the middle.

Yet no discussion in Washington of public broadcasting's programs strays far from political perceptions. Boaz, who describes himself as an avid NPR listener, can cite a variety of anecdotes suggesting public broadcasting's liberal agenda. NPR and PBS reporters are more likely to focus on such topics as gay marriage, the politics of the religious right and environmental destruction, he says, and are less likely to explore issues embraced by conservatives or libertarians, such as the burdens of taxes, the social and economic costs of government regulation, or the number of people who used guns to prevent crimes.

When he was driving home recently, Boaz toggled between WAMU-FM and WETA-FM, the leading public stations in Washington. On one, he heard a commentary by former Clinton administration official Robert Reich. On the other, it was commentary from NPR senior news analyst Daniel Schorr, who often expresses liberal views.

On two other days, Boaz says, NPR's "Morning Edition" featured reports on two left-leaning plays, one written by Reich, the other an anti-Iraq war diatribe by David Hare. "I sincerely doubt that if a conservative writes a play denouncing liberals, which is the opposite of Reich's play, NPR will be rushing to celebrate it," says Boaz.

Further, he says, you can tell something about public broadcasting by who its friends are. When the House was considering draconian cuts in CPB's budget last month, he notes, "left-wing pressure groups" such as MoveOn.org and Common Cause orchestrated a grass-roots campaign that helped generate hundreds of thousands of supportive e-mails and phone calls to Congress.

But that's not to say conservatives have been shut out of public broadcasting. PBS (and educational TV before it) has a long history of conservative-hosted or -oriented shows, starting with William F. Buckley Jr.'s "Firing Line" in 1966. Others include "The McLaughlin Group," "Think Tank With Ben Wattenberg," "Adam Smith's Money World," "Wall Street Week," "Nightly Business Report" and a news discussion program called "National Desk" that featured such conservatives as Fred Barnes and Laura Ingraham. PBS also has distributed miniseries based on the work of William Bennett ("Adventures From the Book of Values"), and one starring former Reagan and Bush I speechwriter Peggy Noonan ("On Values: Talking With Peggy Noonan").

Even so, Gigot, the "Journal Editorial Report" host, charges that public television stacks the deck against conservatives in other ways. He says that PBS-affiliated stations have been reluctant to add his program to their schedules (PBS distributes the show but stations are free to set their own lineups), or broadcast it in pre-dawn time periods. "There's been a conscious decision by stations to run 'Now' [Moyers's former show] but not to run us," he says. "The motivation for that -- well, you can make up your own mind."

NPR and PBS officials say perceptions of bias run in both directions. Many liberals rap PBS for being too "pro-business," says John Wilson, PBS's senior vice president of programming, and for not reporting adequately on labor and small farmers. NPR Vice President Ken Stern says liberal listeners complain to NPR's ombudsman at twice the rate of conservatives. "If I had a nickel for every time I heard us called National Pentagon Radio, I'd be wealthy," he says.

It's hard to make sweeping generalizations; there hasn't been an independent and systematic study of the political content of NPR or PBS programs in years. An informal survey of a handful of PBS and NPR news shows, spearheaded by Tomlinson last year, did find that liberal and anti-Bush administration views dominated a few programs. But Tomlinson declined to release the methodology of the survey, or even the survey itself. When Sen. Byron Dorgan (D-N.D.) forced his hand, Democrats and others inside public broadcasting criticized it as amateurish and flawed.

Public broadcasters instead point to two national surveys of TV viewers commissioned by Tomlinson's CPB in 2002 and 2003 that gave high marks to both PBS and NPR for their news and public-affairs reporting. Conservative suspicions about public broadcasting also haven't been corroborated, so far, by the two veteran journalists hired by CPB in April to serve as ombudsmen and in-house critics; their reports have been filled with praise.

"I'm still waiting for the evidence" of systematic bias, concludes PBS's Wilson. "We can always do better about the diversity of viewpoints and voices, but I don't know anyone who does it better than us."

Viewers and listeners of public broadcasting might be forgiven for wondering what all the fuss is about. Lehrer's news program almost never attracts complaints about fairness, and it's hard to locate the potential for outrage in such programs as "Smokestack Lightning: A Day in the Life of Barbecue." But as long as tax money helps sustain them, the institutions of public broadcasting leave themselves open to attack on any grounds, from any quarter.

"By accepting the government's money, public broadcasters will never be free of government efforts to control or even censor programming," says Adam Thierer, a senior fellow at the conservative Progress and Freedom Foundation in Washington. "I happen to be one of those people who enjoy what's on NPR and PBS. But when public money is involved, it does mean that strings are going to be pulled in one direction or another."

"I'm beginning to think public broadcasting would be better off without public money," says McCauley, author of the book about NPR. Referring to the late San Diego philanthropist who bequeathed $200 million to NPR in 2003, he has an idea for its future: "It needs more Joan Krocs."

"Antiques Roadshow," above, was PBS's most popular show last season. Documentaries on boxer Jack Johnson, left, and musicals (such as "A Chorus Line," below) were also in the top five.The Wall Street Journal's Paul Gigot, right, says talk-show host Tavis Smiley, left, typifies the "center-left" perspective of most PBS personalities. Some conservatives have long seen a liberal tilt at PBS even though, for many years, it aired William F. Buckley Jr. and his "Firing Line."Bill Moyers and "Sesame Street" are two of public television's long-standing icons, but the former finds his role under siege.