While most of their colleagues basked in self-satisfaction over having asked the Rev. Jesse Jackson to lunch, a few members of the Republican National Committee viewed last weekend's activities as an irrelevant exercise.

It is not merely that the flamboyant Rev. Jackson can play no meaningful role in meeting the Republican drive for black support or even that the drive itself may be unrealistic. Rather, the quixotic quest of Republican National Chairman William Brock for black votes is undermining a more realistic search for lower-middle-income white votes on the issue of reverse discrimination. "I think Bill has got the tail wagging the dog," one prominent Republican told us.

This specific complaint leads to a broader question: Has Brock, during his industrious and energetic first year as chairman, missed the point by failing to establish a coherent opposition to the Carter administration?

Even critics do not deny that Brock, becoming chairman after his 1976 re-election defeat as a senator from Tennessee, has generated more purposeful activity at national headquarters than anybody can remember. Local Republican candidates can now look to Washington for more practical help than they ever got in Nixon-Ford days.

But this nuts-and-bolts activity is not matched by a national Republican voice relentlessly hectoring President Carter. National committee members who tried to talk former Treasury Secretary William Simon, inexperienced as a politician but not as an advocate, into taking the chairman's post a year ago were seeking such a voice. They are naturally disappointed in Brock's absence from the news media.

What little news Brock makes concerns not Carter's performance but Republican courting of the black vote. Thus, the only publicity spawned by last weekend's national committee meeting was the luncheon speech by Jackson, whose last political adventure attracting national attention was as a McGovernite at the 1972 Democratic Convention when he helped unseat Richard J. Daley's Illinois delegation.

Even those right-wing Republicans at first unpleasantly surprised by the announcement of Jackson's appearance ended up happy. Besides their pleasure over the unaccustomed publicity, Jackson's emphasis on moral self-help by young blacks delighted their Republicanism.

But Jackson's basic program of massive federal aid to the cities is alien to Republicanism. More to the point, what does Jesse Jackson have to do with black votes? While he probably has more prestige in Los Angeles than in his home base of Chicago, there is nowhere he controls even a precinct.

If the Jackson lunch was a harmless irrelevancy, the overall Brock campaign for blacks could carry serious liabilities. "I told Bill when he started on this that it was okay so long as it didn't detract from our main chance at getting more blue-collar workers," one Republican insider told us. "He told me it wouldn't but he was wrong."

Brock's associates freely admit the quest for the black vote helps explain the chairman's reticence in talking about job and school quotas favoring blacks, or reverse discrimination. That reticence has been an unexpected windfall for Democratic politicans, who expected the worst last fall when Carter overruled his Justice Department to endorse racial counterdiscrimination in the Bakke case.

When asked about the Bakke case, Brock bails out by claiming he cannot comment on a case before the Supreme Court. Forget Bakke , then; what about reverse discrimination in general? Brock replies with the ambiguous Carter formula: supporting affirmative action, opposing quotas. Clearly, the Republican national chairman wants neither to hurt his own campaign for black votes nor to suggest "racism" in the GOP.

A prominent Republican named Gerald R. Ford disagrees. Breakfasting with newsmen in Washington recently, the former President said he is "almost inevitably" asked about the Bakke case. "I take a thoroughly blunt position," he related, explaining he is against quotas. "I think it's unconstitutional, and I think those who advocate it today will regret it in the next decade." Ford added he always gets a "a good response," even at Dillard, a black college in New Orleans.

Has Ford recommended to Brock that he take a similar line on Bakke ? No, he answered, but "that might be a good suggestion." Such a Ford-to-Brock talk might go into other issues stressed by the former President but largely ignored by the national chairman, such as national defense and the strategic arms limitation talks.

But for now, Brock's Republican critics would be happy if he were warned about heading their bedraggled party down a blind alley while sacrificing the possibility of substantial gains.