For one hour last Wednesday evening, the contestants in the race for the U.S. Senate seat debated, with appropriate seriousness, the questions of strategic arms control, NATO forces, trade relations, immigration, Middle East policy and human rights.

The forum arranged by the League of Women Voters for Gov. Edmund G. (Jerry) Brown Jr., the Democratic nominee, and San Diego Mayor Pete Wilson, his Republican opponent, was remarkably devoid of verbal tricks and cheap shots. Both men clearly had prepared well for the confrontation and both spoke with clarity and occasional eloquence.

It was a welcome change from the pattern of a campaign that, like many others this year, has been dominated by 30-second TV spots aimed mainly at denigrating the character, consistency and competence of the opposition.

The only trouble was that if you did not happen to be within range of a San Francisco television station, you had difficulty seeing it.

The debate was carried live by two stations here, but in the massive Los Angeles TV market, where 40 percent of the state's voters live, it was available only on the UHF public television outlet, and there with a two-hour delay.

The commercial stations in Los Angeles -- and in most other cities -- declined to make room for the debate on their schedules. This might be thought of as simply an expression of characteristic Los Angeles disdain for anything originating in San Francisco. But, as of now, none of the stations is planning to televise Monday's second and final debate -- which is being held in Los Angeles.

What the broadcasters are saying, in essence, is that their normal commercial fare is more important than the exposure of their hge audiences to the views of the men whose policies may decide the ratification of future nuclear weapons treaties or the shape of future defense budgets.

This is not a parochial matter. The three main channels in Los Angeles are owned and operated by the national networks, and their management decisions reflect a set of values endemic in that industry. Complaints of lack of television coverage of the campaign have been heard in many states this year.

These stations are huge profit centers, with some of the profits in an election year coming from the millions of dollars of individual political contributions that are funneled directly into television advertising.

Television swallows those dollars and then, often, on its news shows and commentaries, joins the denunciation of the distorted and negative messages of the 30-second ads it runs.

The response of television executives to this kind of complaint is that they cover the highlights of the debate on their news shows, just as newspapers do in their columns. That is fine, as far as it goes.

But it is clear that the value of a campaign debate, like the value of a televised presidential press conference, is the rare opportunity the voters have to watch public men answer questions at length. They can hear the candidates' views, not in capsule but in the round, and form their own conclusions on the men and the issues.

Voters who had doubts about Brown and Wilson would, I think, have been pleased by the knowledge they displayed and the calm, reasoned way they presented their views.

Those voters would have learned that there is broad agreement between them on the next steps in the Middle East, that they share an aversion toward protectionist measures in foreign trade and are clearly conscious of the domestic and foreign pressures that must be adjusted in our immigration policy.

More important, they would have heard them define their differences on the best strategy for achieving a nuclear arms agreement and the best way to defend Western Europe in the next decade. The debate over the appropriate role of conventional and nuclear arms -- the costs and the risks of both -- is about as important as any issue likely to face the Senate in the coming years.

But voters in Los Angeles did not see that debate. On the CBS affiliate, they saw an episode of "Seven Brides for Seven Brothers," in which "a romance between Crane and a veterinarian turns into a dilemma when the vet is awarded a medical internship that will separate them," to quote the listing in the Los Angeles Times.

On the NBC affiliate, it was "Real People," with "the salute to Chicago," including "baseball legends of Wrigley Field, Mayor Jane Byrne . . . a cheeseburger emporium made famous by "Saturday Night Live," a man who designs Miss America Swimsuits, a cat that predicts the weather," and, as the saying goes, other wonders too numerous to catalog.

On the ABC affiliate, it was the 1968 Rock Hudson film, "Ice Station Zebra," which presumably would have melted if its showing had been delayed after 14 years.

I would like to hear the explanations of the television executives who blanked out the debate for these programs, and I will share their comments with you if and when they arrive.