President Reagan's black appointees, says one of them, is the administration's "best-kept secret."

Ronald N. Langston, a 32-year-old official at the Department of Health and Human Services, is convinced that he and scores of other well-placed administration blacks should be on the campaign trail, selling a second Reagan term as the best hope for getting what black America needs: a new focus on economic self-sufficiency.

Instead, he says, he and his black colleagues have been "grossly underutilized" because of a false assumption that black voters simply aren't available to the Republican Party.

"They (influential white Republicans in Washington) think it's not cost-effective to send us out because blacks aren't going to vote for Republicans anyway. I've heard it too many times: 'Ron, we're just not going to reap any benefit from going after the black vote. They have proven to us beyond a reasonable doubt that they don't like us, they don't want us, that they'll never vote for us. So why go out there and try to get them?'

In other words, Langston thinks it is pessimism that prevents his party from sending him and other black Reagan appointees after black votes.

Would he entertain an alternative explanation? I offered the possibility that going after black votes implies a change in style which the GOP leadership doesn't want to make. That is, while the party's influential leaders like to have a few black appointees around (as protection against charges of racism) and are quite prepared to take any black voters who happen to agree with what the Reagan administration is about, they have no interest in modifying their campaign so as to attract additional black voters.

"I really don't think so," he says. The former legislative aide to Sen. Roger Jepsen (R-Iowa) says he has "been in the back rooms sometimes when they forget I'm there, and what it comes down to is that it will take a commitment, a plan, a schedule, an approach, all of which won't reap any real benefit, so why drop the money and the time?"

But the problem goes beyond campaign decisions. I reminded Langston of the bewilderment of Washington's best-known black Republicans -- people such as Art Fletcher, George Haley and the late Sam Jackson -- upon learning, early in the Reagan administration, that they had no access to senior staff, that no one in authority sought either their service or their views. These were Republicans with solid conservative credentials, many of whom had come here to join the Nixon administration, who nevertheless were broadly respected by non-Republican blacks. They could have been an unusually effective bridge between the GOP and the black electorate. But they were never tapped. Does Langston wonder why?

"I thought that was a mistake," he says, "but I don't think it was because the party didn't want more blacks. In any case, the party is bigger than the present administration, though I support the president completely. I mean, I didn't become a Republican because of Reagan. Like most blacks in the party, I became a Republican because of my experience with Republicans in my home state (Iowa) and because of the party's history, its goals and its principles.

"That's what we need to be selling. The civil rights period provided a lot of us with opportunity, but we now have to move beyond that toward self-sufficiency. I think the Republican approach is more appropriate for that goal than the Democratic idea of making black people comfortable in their poverty."

If the party's product is as good as Langston supposes, and if Reagan's black appointees are willing to market it, why haven't they been asked to join the sales force?

Langley shakes his head in frustration and says again: "We're the best- kept secret of this administration."

Could it be that somebody likes it that way?