Ever wonder why you are seeing so many anti-drunk-driving ads on television these days? In part, it is because broadcasters, who run these announcements free, have been moved by a spirit of public service. The other part is more interesting.

Last year a radical idea to attack alcoholism began getting a sympathetic hearing in Congress: ban alcohol ads from TV and radio. The logic is simple. A similar cigarette ban 15 years ago contributed significantly to deglamorizing smoking and to a subsequent drop in cigarette consumption. Deny a habit, such as smoking, its crucial niche in the collective unconscious that is television, and it becomes vulnerable to appeals to reason.

That idea, applied to alcohol, sent two powerful industries -- beer and wine producers and broadcasters -- into a panic. The National Association of Broadcasters made defeating the alcohol ban its top legislative priority for 1985. The scare also concentrated some industry minds on the need for good works, so as not to appear too prepared to override the public welfare for their own. Hence the broadcasters' recent burst of ostentatious good citizenship.

In lobbying on Capitol Hill, however, ostentation and good citizenship are less valued. There, in little noticed hearings, most recently last Tuesday, the brewers and broadcasters have been counterattacking. They present an interesting case.

It starts with the "Who me?" defense, founded on the improbable claim that beer ads do not promote drinking. Advertising merely promotes brand-switching, explains Donald Shea, president of the U.S. Brewers Association. It does not increase consumption.

Can anyone believe that advertising is designed to get you to love Bud but not beer? Grasping a distinction so metaphysical is hard. Believing it is harder. Because if is true that advertising does not encourage people (especially first- timers, such as kids) to drink, and drink more, then the brewers should be delighted with a ban. They should welcome an externally imposed end to a ruinously expensive advertising competition that only impoverishes the industry, since it produces no new customers. Come on, guys.

And even if the ads are not intended to make people thirstier, that is still their effect. Advertising is the business of creating associations. We think ourselves sophisticated enough to see through ads, but manufacturers pay hugely for them because they work. The association of alcohol with good times and camaraderie, washed into the brain inning after inning, leaves an imprint. (I still occasionally break out into the jingle for Ballantine beer, radio sponsor of the Yankees when I was 10.) That imprint -- an idealized image of the tavern culture, all buxom and boisterous and bright -- helps a youngster persevere past the bitter first taste of booze for the rewards that lie ahead. What high school junior doesn't long for Miller time?

When the "Who me?" defense collapses, the "Watch out!" line takes over. Here the argument is social cost. The broadcasters warn that we will suffer at the hands of the new prohibitionists posing as do-gooders. Programming will be hurt. "There is a good chance that we would have to drop coverage of sporting events such as golf and basketball," warns a senior NBC official. So, on one side of the scale, some of the 20,000 killed yearly by drunk drivers and some of the $100 billion spent on alcoholism; on the other, some TV golf and basketball. You choose.

If you choose golf, the broadcasters rest. If you don't, they have a last defense. It is the "My goodness" defense. My goodness: you want to tamper with the First Amendment!

Is there an unworthy cause in the land that will not try a free speech defense? In fact, we tamper with free speech all the time, especially in mass media. The censorship codes for television are elaborate and strict: no four- letter words, no nudity, no Marlboro man. Speech is massively controlled on mass media for good reason: it has mass effects, some of them bad. There are certain things we agree we don't want television promoting, and we are willing to make TV speech a bit less free as a consequence.

When it comes to censorship on television, the question is not whether, but for what. The what cannot be trivial. It must be important, as important as deglamorizing smoking. It is hard to see why deglamorizing alcohol fails to meet that standard.

Congress, however, never one for crusades, is already backing off this one. The ban campaign has peaked. Under severe pressure, it has given way to a compromise that leaves intact current ads but mandates counter-advertising to show alcohol's dangers. Even this exercise in moderation hasn't much of a chance. The most the 99th Congress is likely to produce is a call for a one-year study to determine whether alcohol advertising promotes consumption. If you need a study to tell you that, you can't be too interested in the answer. The Tobacco Institute, remember, is still studying the "hypothesis" that smoking causes cancer.

Annals of Congress: another good little idea, steamrollered.