Sheldon and Anita Drobny’s proposal to fund a liberal commercial talk radio alternative to Rush Limbaugh, Sean Hannity, Laura Ingraham et al. has, if nothing else, gotten lots of attention. A Google search on “Liberal talk radio” yields dozens of news articles posted just in the last hour — probably less now that the war in Iraq has begun, but still. And conservative commentators haven’t been able to leave the story alone.

David Limbaugh (“Talk Radio — Liberals Don’t Have a Clue,” Townhall.com, March 5); Jeff Jacoby (“Liberal Talk Radio Won’t Work,” Boston Globe, March 2); and Jonah Goldberg (“Liberal Talk Radio? Keep Laughing,” Townhall.com, February 26) have all written essentially the same column, making the same points, and citing the same examples of liberal talk failure (Jim Hightower, Mario Cuomo).

But they’re looking at the wrong economic model. In fact, liberal talk radio is alive, kicking, and very, very good — on the taxpayer — and listener-subsidized National Public Radio network.

I can hear the protests: “But that’s not fair!” Of course it is. The rules exist, NPR exists, and we should no more fault liberals for taking advantage of a subsidized medium than we fault Christian radio programs like “Truths That Transform” or “Focus on the Family” for soliciting their sponsorship directly from their listeners, according to their rules.

Granted, the difference between NPR and commercial radio is profound. Do you know (many conservatives do not) Rush Limbaugh’s stated goal for his radio program? “To charge the highest possible extortionate advertising rates.” Rush says this with high good humor, but he means every word. And he owes his considerable success to his not inconsiderable ability to schmooze and nurture advertisers (something also widely ignored by commentators). Select Comfort Sleep Number Bed, anybody?

But that method — swapping off a designated number of advertising minutes per hour between program and carrying stations — requires a high degree of what admen call “efficiency.” In the NPR model, financial contributions come in directly, and efficiency doesn’t come into play.

But beyond that, the conservative critique of liberal talk ignores a couple of major, 15-year trends in non-music radio: The transformation of the NPR network by a cohort of talk shows, gradually changing over the NPR profile from classical music and jazz to talk in markets around the country. And the utter trashing of conventional AM news radio as a useful medium for news.

I saw both trends begin in Boston in the 1990s. WBUR, the influential NPR station of Boston University, now calls itself “Your NPR news and talk station.” And so it is, with “The Connection” in the morning, “Here and Now” at noon, “Talk of the Nation” (from New York) in the afternoon, and “On Point” in the evening. The shows are sharp, have good production values, and are expertly moderated. Granted, they can make you sick. (I once had to listen to an hour of Noam Chomsky on “The Connection” while I was up a ladder painting a bathroom.) But they do well at what they do, and they have a devoted audience.

More important, these shows have taken over NPR station programming throughout the country, sometimes engendering resistance from traditional listeners who would rather have their Mozart or their Miles back. But it has been happening. Talk is the new face of NPR.

At the same time, competition from conventional AM news has gotten weaker and weaker. Blame it on traffic. In the 1980s some time, KNX 1070 in Los Angeles moved from broadcasting traffic reports only during rush hour to airing them every 10 minutes all day long. Then weather moved in, just as often. Sports took up 150 seconds. Subtract 120-plus seconds of commercials, and that left a news hole only three minutes long in every ten-minute rotation, most filled with reports so stupid that a high school junior could have made up something just as interesting. Around the country, in major metro areas, other stations followed suit — or even got worse. WEEI in Boston used to stick an open mike in front of a TV tuned to CNN Headline News, then send everybody at the station home at 10 p.m.

Whatever, now there’s no reason to listen to AM news except for a road report as you drive in to work. And NPR, leveraging on the audiences for “Morning Edition” and “All Things Considered,” has expertly stepped into the vacuum.

Jacoby, Limbaugh, Goldberg, and other conservative pundits are right: Liberal talk radio won’t work on commercial frequencies. But that’s not because there’s no audience. It’s because the liberal talk audience has plenty to listen to. They don’t need any more. Plus, that audience is sewed up tight. What do they need with their own Imus? AM? What’s that? Isn’t that where you listen to, like, baseball?

Now if you want to talk about de-funding the Corporation for Public Broadcasting …