PBS's thorny issue: whether to expand the MacNeil/Lehrer Report

Public television's most controversial programming decision ever - concerning a daily one-hour ''MacNeil/Lehrer Report'' - is causing great soul-searching in and out of PBS.

What appears to be a programming matter actually involves fundamental questions about the ways public TV can influence the news business - possibly pushing commercial TV closer to its own one-hour news programs - as well as concerns about the place of corporate sponsors in such programming.

According to Robert MacNeil, an AT&T $10 million production grant for the program would be the largest single corporate commitment in public TV. In addition, AT&T pledged to spend $2 million more on advertising and promotion of the show.

The decision of whether or not to accept the offer - to be matched by a similar amount from the Corporation for Public Broadcasting (CPB) and around 300 PBS-affiliated stations - will probably come up for a preliminary vote by program directors on Monday, with a more binding vote due later in the year.

At last week's annual PBS Program Fair - at which station program managers gathered here to consider which shows they will buy for the upcoming year - the idea of a nightly one-hour ''MacNeil/Lehrer Report'' was the subject most often discussed.

Some station programmers felt they were being ''brainwashed'' by the MacNeil-Lehrer team, which attended and made two major presentations. In addition, there was a luncheon sponsored by AT&T and statements of support for the hour-long show by CPB President Edward Pfister and PBS President Lawrence Grossman.

There was some question as to whether the MacNeil-Lehrer combination presented a strong and pleasant enough image to attract viewers five nights a week - and some resentment that in their presentation, Mr. MacNeil and Jim Lehrer hinted they might not consent to return with their popular half-hour nightly show if the programmers rejected their suggestion for a one-hour nightly show. The half-hour show was not even submitted as a possibility - in what appeared to be an attempt to pressure the programmers into accepting the one-hour concept.

At first, it was suggested that the hour be aired from 8 to 9 p.m. every night, but the plan was altered so that, if accepted, it would probably be available for airing at 6 p.m., 7 p.m., 8 p.m., or even later, leaving the choice to the individual stations.

According to the presentation made by Messrs. MacNeil and Lehrer, the new show would be very different from the current ''MacNeil/Lehrer Report,'' which to a great extent offers one topic discussed by ''talking head'' experts. ''Gone would be the automatic one-story-a-night formula,'' they said in their presentation. ''On some nights there might be two, three, four, or more stories. On rare occasions when there was a supreme news event, the entire program might be devoted to various aspects of a single story.''

And there would be great flexibility in format - besides ''talking head'' experts, there would be more film and tape pieces, more documentaries. They even answered the accusation that they were ''humorless'' by promising there would be a place for ''humor and delight.''

In a later paper they delivered which delved more extensively into the ''news for grownups'' program plan, MacNeil and Lehrer indicated that the new show would be ''a one-hour nightly news magazine.'' Not like ''60 Minutes,'' ''20/20, '' or ''PM Magazine,'' they stressed, but ''first and foremost, a news program - and the news, whether hard or soft, will not be frivolous.''

While the $12 million grant would seem to be altruistic on the surface, the fact is that the motives of AT&T should be viewed with some wariness. It has long been rumored that the company, which is deeply involved in the ''hardware'' of news - renting out its wires and its satellites - would like very much to be involved in the ''software'' of news as well - newspapers, videotext, teletext, and so forth. But it has been prevented from doing so by anti-trust laws and FCC regulations.

By underwriting this nightly show, AT&T might, in effect, be getting into the business of news dissemination through a ''back door.'' Where that would lead, remains to be seen. But it is a matter with major implications in the overall news structure of the nation.

William Mullane, assistant vice-president of AT&T public relations, was incensed when informed of the questioning of AT&T motivation. ''That is preposterous,'' he told the Monitor. ''AT&T is too big to go through the back door of anything. We do not have any intention of getting into news dissemination, and I don't know how many times we have to say it to get people to believe us.''

But with the current experiments in ''enhanced underwriter credits'' and actual commercials on PBS, there is the chance that the one-hour ''MacNeil/Lehrer Report'' might seem more like ''The AT&T Report.'' However, AT&T is currently a major underwriter for the half-hour show, and there has been no such over-identification on the program, although a one-hour, widely promoted version could change all that.

Aware of that potential for criticism, Mr. Grossman, the PBS president, when questioned about it by the Monitor, stressed that he was ''impressed at their sensitivity and sophistication about their own underwriting.'' He added that ''I can assure doubters that there will be no involvement or interference by AT&T tolerated in the editorial content of the show.''

Mr. Grossman does not underestimate the importance of the show in the future of PBS. He makes it clear, however, that if it should fail, he does not want it to be an irreparable setback for public broadcasting. Therefore, he says: ''I want it billed as a year-long experiment, with nobody committed to go beyond that year. We are going into uncharted waters, and it would be inappropriate to risk everything on it.''

Mr. MacNeil told the Monitor he is quite willing to accept at face value the words of Mr. Mullane, who said at the AT&T Washington luncheon that his company simply wanted ''to be associated with excellence. . . .'' Mr. MacNeil also indicated that he and Mr. Lehrer have still not decided what course they will take if the one-hour plan is rejected.

There have been suggestions for a compromise - continue the nightly half-hour show and add a weekend one-hour roundup. But MacNeil and Lehrer refuse to even consider that expanded variation. The program will have to be one hour, they imply. Many PBS stations resent that sort of ultimatum.

The big question that might have to be faced: Would MacNeil and Lehrer agree to continue the existing half-hour show, or would they be so piqued that they would search for another outlet for what has become one of PBS's most prestigious programs?