THERE ARE WEEKS to go until "The Day After," but already the ABC movie about nuclear war is proving explosive. It could well become the most politicized entertainment program ever seen on network television, a fact that has jitters spreading like a virus through ABC executive suites.

The film depicts in agonized, explicit--and, ABC spokesmen point out, heavily researched--detail the effects a nuclear attack would have on Kansas City and surrounding towns. Those closest to the two nuclear bombs that hit the city itself are vaporized or burned alive by the firestorm on screen (one woman looks down to see her legs engulfed in flames that quickly consume the rest of her); those in outlying cities like Lawrence, Kan., where much of the movie takes place and was filmed, suffer the ravages of radiation sickness from nuclear fallout.

Immediately or gradually, virtually everybody in the movie either dies or clearly is going to die. It is nearly impossible to imagine anyone coming away from this crushingly powerful film unstunned.

What remains to be seen is whether this will be a consciousness-raising experience for the viewing nation or a consciousness-battering one. ABC's nervousness is inspired not so much by the film itself as by the ways pro- and anti-disarmament groups will attempt to use it for their own ends, especially on the pro-disarmament side. Josh Baran, national media coordinator for a project called Target Kansas City/Let Lawrence Live, says from his Berkeley, Calif., headquarters that candlelight vigils and marches will be held in Kansas City and Lawrence the night of the telecast, Nov. 20, to help make the film the centerpiece of a renewed anti-nuke drive.

Baran says there will also be "tens of thousands of group viewings" of the film that night sponsored by anti-nuclear organizations; an ABC spokesman estimates there are 900 anti-nuclear groups hoping to use the film as support for their cause. Meanwhile, claims Baran, "the radical right is mounting a major offensive against the movie," labeling it left-wing propaganda designed to discredit President Reagan's crusade for heavy defense spending and to "undermine our nation's security."

The film will air not long before the first Pershing II missiles are deployed in West Germany and about the time widespread demonstrations against the missiles are expected to be organized in Europe. "The Day After" may find itself at the center of a furor unlike anything commercial television has seen since CBS broadcast, with great reluctance and after much delay, the anti-Vietnam war play "Sticks and Bones," by David Rabe, in 1973.

The fact that the telecast is engendering this kind of tumult already could itself be seen as a sign that the mind-set of the country is shifting back to a '50s Cold War mentality, a drift accelerated by the Soviet attack on a South Korean commercial airliner last month and by the Reagan administration's perceived preference for swords over plowshares. Suddenly the Soviet Union is "evil" again, and Johnny Carson feels the times are right for jokes about the Russians along the lines of his previous jokes about Iranians. He recently joked that an airport metal detector was set off by "Yuri Andropov's heart."

William F. Buckley's National Review chose to view the telecast of "The Day After" with worldly sarcasm, in an unsigned piece headlined "ABC-TV Backs Deterrence" that concluded, "The producers at ABC obviously want to impress upon us just what might happen if our deterrent becomes unconvincing, tempting the Soviets to treat Lawrence, Kan., as if it were a Korean airplane. Three cheers for ABC-TV."

Nicholas Meyer, the director of the film (and of such theatrical films as "Star Trek II: The Wrath of Khan"), says from Los Angeles that he is unhappy about the advance uproar over his film. "I deplore it on both sides, because the people talking about the film haven't seen it," he says. "However well-intentioned the various factions may be, they're trying to affect the credibility of the film, yea or nay, in the minds of those we expect just to watch it. They're trying to make up the minds of viewers beforehand."

ABC has not yet officially screened the film for the press because the network wants its affiliates to be able to see it first. The "world premiere" showing of "The Day After" takes place tomorrow in Lawrence, where about 3,000 locals who served as extras in the production will have the bizarre experience of watching as their town is destroyed and they suffer and die.

In fact, though, there have been an uncountable number of unofficial screenings of the film not sanctioned by ABC. There appear to be more bootleg copies of "The Day After" than of "E.T.," but apparently only the pro-freeze or pro-disarmament troops have seen them, a fact that angers sources on the other side. One says that, if necessary, "I'll go to Lawrence, Kansas, to see the son of a bitch."

And John M. Fisher, president of the American Security Council, a group that advocates "peace through strength," said yesterday he will ask ABC today if he or a member of his group could have "a pass" to the showing in Lawrence, since ABC had promised him a screening of the film.

Fisher also said that ABC public relations executives requested a meeting with him early in September, because they felt, says Fisher, "that the nuclear freezers were coopting this film as their own." Fisher says the ABC executives insisted the film was not a political statement but that he told them, "You have said with this film that deterrence failed. It's worked a long time, but you have said it's failed, and that's a political statement." While innumerable pro-freeze and pro-disarmament groups have seen the film, Fisher says, to his knowledge no one in any of the 150 organizations that make up the Coalition for Peace Through Strength has been able to see it, officially or unofficially.

On the pro-freeze side, Rep. Edward J. Markey (D-Mass.) says he saw the film six weeks ago but adds, "I can't tell you how I saw it." Markey, cosponsor with Sen. Edward M. Kennedy (D-Mass.) of a 1982 nuclear freeze resolution, calls the film "a great movie," says "public opinion will be influenced, I think, positively by this" and thinks that the film will "help move the administration toward signing a treaty" with the Soviets.

Meyer counters that the version of the film seen by Markey and others is not the final cut to be shown by ABC. The film, which stars Jason Robards, Jobeth Williams, John Lithgow and John Cullum, has gone through many alterations since Meyer first read the script in May 1982. Originally planned as a two-night, four-hour telecast to be seen last May, the film was mysteriously scrubbed from the schedule by ABC last season and has now been edited down to a running time of two hours and five minutes (with commercials, an air time of about two hours and 15 minutes).

A popular rumor had it that the White House had pressured ABC executives to delay or dilute the film. ABC spokesman Dick Connelly says from New York, "As far as I know, that's not true." And ABC Circle Films president Brandon Stoddard has said, "I know nothing about such pressures and I haven't heard anything about them." White House spokesmen would not respond to inquiries about the rumor.

The cutting was made not to make the film more palatable or less anti-nuclear, ABC spokesmen say, but to tighten it. Meyer confirms this position. He says ABC originally needed a two-night run in order to recoup the $7 million production costs for the film but that he always considered the script padded with extraneous "filler" about the fates of various characters. In addition, says Meyer, "I didn't think anybody was going to tune in for Night Two of Armageddon."

Meyer does not say why ABC suddenly decided it didn't need a two-night run of the film, but he says the film has not been weakened by the editing. "There is no sort of political hoopla involved," says Meyer. "We argued a lot--that's usual for TV movies. They do what they want, and the director is told to get lost. But we argued not contents, but esthetics. They haven't betrayed us. I'm not betrayed. This is the film I set out to make. I can't say they betrayed the intent of the movie in any way."

Advertisers have not been beating down ABC's doors to buy commercial spots on the show. Network spokesmen keep saying they are about to announce major corporate sponsorship of the programming, but none has been announced so far. Care will be taken in the placement of commercials within so grim a drama, network sources say.

ABC spokesmen deny the network is nervous or panicky about the film. But it may be a sign of nervousness that ABC has taken the extraordinary step of scheduling a special edition of the ABC News "Viewpoint" program, anchored by Ted Koppel, immediately following the telecast. Connelly says this was done because "we feel the issues raised in the film should be discussed, so we are providing the forum. We think people will want commentary and analysis."

Asked if the network is "scared," Meyer replies, "Sure," and suggests there is still the possibility ABC will choose not to show the film. "I'll believe it when I see it, that it's on the air," says Meyer, to which an ABC spokesman counters that the film will "absolutely" be shown. Baran says ABC's nervousness can be gauged by the small amount of publicity it has so far disseminated about the film. "With 'Winds of War,' they started promoting six months early," Baran says. "Their commitment is not as strong as it was to 'Winds of War.' They're just scared."

And Robert Papazian, producer of the film, says from his office in Los Angeles, "Yes, they're nervous--because anyone that takes a chance is going to be nervous. But they are taking the chance, and I take my hat off to them for that." Meyer adds, "In one of my books, I think it was 'The Seven-Per-Cent Solution,' I wrote that 'bravery consists of being scared stiff, and going ahead and doing something anyway.' I think that is what's happening here. I know the executives are very proud of the film. They're scared of it, but proud of it. They've called it the most important movie they've ever made."

Whether the "radical right" counter-offensive envisioned by Baran is actually taking shape remains to be seen, but already a New York newspaper has denounced the film as a political act, one that amounts to ABC's doing Yuri Andropov's work for him. Meyer calls the charge "the most McCarthyist thing" and Papazian says, "That's a ridiculous statement." The script for the film, by Edward Hume, never specifies which side, the Russians or the Americans, fired the first missiles, and Papazian says the film takes no political stance. "It's like we've done a film about cancer, and cancer can kill, and we are simply saying, 'Avoid cancer at all costs.' "

Fisher feels, however, that it's not that simple. "Nuclear war and the seriousness of it is the starting point for either side in this debate," Fisher says. "Nobody is for nuclear war. But the nuclear freeze side says, 'Nuclear war is terrible and therefore you should have a freeze.'

"The people on the other side have had an enormous lead time to prepare for this film--some of them saw it as much as two months ago--and they seem to be uniformly enthusiastic about it, so I wonder if we should be enthusiastic."

Baran hopes to get some of those involved in making the film to participate in the candlelight vigils, marches and rallies. Nothing would please ABC less. Meyer says he is turning down Baran's request and will make no statement about his own feelings on nuclear issues until after Nov. 20. "I have no wish to alienate that portion of the viewing audience that will perceive this film as the facts as we interpret them," Meyer says. "I don't want a conservative backlash saying 'Oh, this is just the Jews in Hollywood, this is just liberals in Hollywood, mounting their soapbox.' "

The subject of nuclear war is not precisely new to prime-time television. In the late 1950s, "Playhouse 90" aired an adaptation of Pat Frank's doomsday novel "Alas, Babylon" that included a scene of supermarket panic much like one in "The Day After." Rod Serling ended the world more than once on "The Twilight Zone."

In recent years, CBS nuked and destroyed Omaha with special effects as part of its five-part documentary "The Defense of the United States"; John Chancellor walked around Missouri and told viewers what effects a nuclear strike would have on the area for an NBC News documentary on the Salt II talks in 1979; last year, NBC televised, but badly bungled the promotion of, a two-part movie called "World War III" that ended with president Rock Hudson ordering up the missiles and weeping as he did so; and this year, NBC aired the Emmy Award-winning "Special Bulletin," which included the simulated nuclear destruction of Charleston, S.C. In that one, anti-nuclear activists were the ones who set off the bomb.

After all this--and such nuclear-themed theatrical films as this summer's smash hit "WarGames"--why should there be such hubbub over the ABC film? Meyer thinks it's because "The Day After" shows nuclear war's effects on typical middle-class Americans, not on generals in war rooms. "I have a general sense that nuclear war as depicted on the screen was always distilled in some way," Meyer says. "In 'Dr. Strangelove,' it was distilled with humor. In 'On the Beach' with distance the film was set in Australia and in 'Special Bulletin,' through the devices of TV journalism. Our film is an attempt to treat it without any distillation whatsoever, served up in a totally familiar format: the good old TV movie."

Rep. Markey says the film will have not only emotional but political impact. "What this movie does is put the lie to the whole notion of 'limited nuclear war' for 25 million viewers in one swat," says Markey. "Support for the president's 'peace-through-strength' program is centered in the Midwest. But when people in Kansas and vicinity--Arkansas through the Dakotas, that half-moon path where our ICBMs are planted--see this film, they'll never again think of fallout shelters as a way of protecting themselves in a nuclear war.

"The film takes the whole issue out of the abstract and makes it very understandable for people, not just for experts. The single greatest problem we have in this area is our natural deference to 'experts.' I think the film's most profound effect will be on people who have been deferring to military decisions and Pentagon decisions, on nuclear issues--ordinary people who've been listening to the president on this issue."

Markey asks and answers the question, "Will people want a mutually verifiable arms treaty after they see this movie? Yes." And then he is asked if it wouldn't be nice for the Russians to be able to see such a movie, too. "Would that it could be shown in the Soviet Union," he says. "But the alternative would be that no country does anything to educate itself on this. Otherwise there will come an inevitable time--20, 25 years from now--that we have the holocaust."

There is much in the film that is terrifying, and not just in the gruesome details of nuclear destruction. The film includes scenes in which people of Kansas look out their windows and see the ICBMs being launched into the sky. One shot has a stadium full of people watching a football game in the foreground while missiles streak into the sky above them, on their way to the Soviet Union. Anne Kronenberg, executive director of the Nuclear Freeze Foundation headquartered here, saw a bootleg copy of the film recently. "Oh God, I thought it was very powerful," she says. "I kept having nightmares all week."

Baran says ABC should welcome his efforts to organize forums and meetings keyed to the broadcast, not be frightened by them. "The film leaves people overwhelmed," he says. "It leaves people with no hope. Millions of kids will be watching, and who needs 10 million kids with nightmares? We don't want this film to be a preview of coming attractions. We're offering outlets for action, ways that people can make themselves heard and learn about the issue. Because the way we feel about it is, it's still The Day Before, and there's still time to do something about it."

Meyer says, "I didn't want to make this movie. I wanted to get on with my career, go on dates, have a good time. I did it to be a Boy Scout, to do my good deed for the day. I did this to be a good citizen; I thought it was a civic responsibility." Papazian says, "It was a very difficult project to do, it was a very difficult project to produce, to get over the obstacles of research and so on, and it's something one can turn back on and say, 'I've contributed,' and I think that's what makes me the happiest. Because very few people can say that." CAPTION: Picture 1, Antonie Becker looks on in terror and disbelief as nuclear missiles streak toward the Kansas countryside in ABC's "The Day After." "The Day After," Copyright (c) 1983, by ABC; Picture 2, Nuclear blast; Picture 3, Jason Robards in ABC's "The Day After"