FOR THE MORE than 20 million listeners who tune in to National Public Radio at least once a week, the authoritative presence of such mainstays as Bob Edwards and Linda Wertheimer has never been more essential than since September 11.

But for local station managers such as Jane Christo, who runs New England’s largest NPR affiliate, WBUR Radio (90.9 FM), it’s rarely been harder to pay for that news.

Just a month ago, Christo told me she was going to broadcast first and figure out how to pay for it later. "We are overspending our budget, and we don’t know where the money is coming from. But we have to spend whatever is necessary," she said. "There’s no time in my lifetime that this has ever been more important" (see "Don’t Quote Me," News and Features, October 26).

Barely three weeks later, Christo announced what she described as the first layoffs in her operation’s history. Corporate underwriting — that is, those brief, low-key advertisements that have been popping up with increasing regularity in recent years — was down 35 percent. Nine people were let go, six from WBUR and three from its sister station in Providence, WRNI. An ’RNI public-affairs show, One Union Station, has been canceled, although a retooled version may pop up next year.

The cutbacks at WBUR — one of the largest and most admired of the country’s approximately 600 public radio stations — says something important about what’s going on in public radio generally. Following efforts by Republicans such as Ronald Reagan and Newt Gingrich to slash or even eliminate taxpayer subsidies to public radio and television stations, public broadcasters reinvented themselves by switching to what is essentially a privatized, nonprofit model.

Public broadcasting today is largely paid for by affluent, well-educated viewers and listeners and the businesses that wish to reach them. This evolution has been especially dramatic for public radio, which, unlike public TV, has a captive audience — millions of commuters trapped in their cars — and a clear mission to focus on news and public affairs (see "Bobos in Radioland," News and Features, April 27).

Never has public radio been better, or more popular, than it is right now. Unfortunately, the commercialism that made modern public radio possible now threatens to break budgets at a time when the medium itself is needed the most. The question is whether this is just a momentary blip, or if public radio’s fat and happy days are about to be followed by some long-term financial reckoning.

THE CUTBACKS at WBUR will not affect Christo’s ability to run NPR’s signature newscasts, Morning Edition and All Things Considered. But they will certainly harm local-news coverage, and could possibly set back her ambitious agenda of developing local programming that can be offered nationally, such as The Connection, a cerebral interview-and-talk show that’s carried by NPR on about 50 stations, or Only a Game, a weekend sports show.

"Look, if there’s a downturn in the economy, of course we’re going to suffer, but everybody suffers," Christo said in an interview last week. "I think that we can still do excellent coverage of the war. I think we’re doing some of our best work right now. I think it’s only fair that we have to watch our money. After all, the listeners give it to us."

But the listeners — the public in public radio, in other words — are not an issue in WBUR’s budget woes. In fact, the on-air portion of the station’s fall fundraiser pulled in some $540,000, which was $140,000 above its goal — a testament to people’s willingness to pay for high-quality news and information during a time of national crisis. Nor is the federal government diverting its limited funds to other, more pressing needs; in any case, only about $1.2 million of the station’s $20 million budget comes from federal tax dollars.

Rather, the budget squeeze came about because of a precipitous drop in corporate underwriting. At WBUR, the sums raised from listeners ($8 million last year) and underwriters ($7.3 million) are almost equal. So when ’BUR suddenly found that funding from its recession-battered corporate angels had fallen off a cliff, Christo’s October bravado quickly gave way to her November pragmatism.

According to Doug Eichten, president of Development Exchange Inc. (DEI), which helps public radio stations raise money, the dilemma that’s facing ’BUR epitomizes what’s going on in other major markets: an increase in listener contributions on the order of 25 percent that is more than offset by a collapse in corporate underwriting, related more to the disappearance of the dot-com economy than to the terrorist attacks.

"That was and should have been seen as something that you just can’t count on the way you could count on local support," says Eichten. "There was an over-reliance on some of the support from major corporations."

The flip side, Eichten adds, is that stations whose corporate underwriting comes mainly from local, long-established businesses have hardly been affected at all.

Take, for instance, the case of WFCR Radio (88.5 FM), at UMass Amherst. According to general manager Martin Miller, underwriting fell apart in October — yet already there are signs of its coming back. Miller has until next June to line up $750,000 in underwriting for the following fiscal year — and he’s received $550,000 in commitments. "We’re in pretty good shape," he says. "Anything can happen, as we saw. Which is why individual gifts become more and more important." (WFCR, like most public stations, pays for about half its budget with individual-listener contributions.)

For the moment, at least, finances are also holding steady at The World, a daily, hourlong newsmagazine show jointly produced by WGBH Radio, Public Radio International (a smaller rival of NPR), and the BBC. In part, says executive producer Bob Ferrante, that’s because The World had already invested most of its resources in foreign coverage. "It’s a little different for us than other operations because the world is our beat anyway. It’s just a concentration of resources in a different part of the world," he says. But he concedes that covering a war brings with it unanticipated costs, noting, "Things are already tight. We’re going to have an overage, and I’m going to have to pay the piper."

Unlike at WBUR, The World’s $5 million annual budget was in place at the beginning of the current fiscal year, on July 1. For Ferrante, then, the question is whether underwriters will stick with the show — or increase their commitment if necessary — as the dawn of the next fiscal year approaches. At the same time, The World has added 12 US stations (it now has 142) since September 11, which means more income to offset some of those increased expenses.

"You’re running a race against the bill collector," Ferrante says. "We’re okay for now — and you can put that in capital letters, FOR NOW."