A few months ago, the 1984 Campaign Award for the Single Most Licentious Political Performance in a Supporting Role seemed safely in the hands of U.N. Ambassador Jeane Kirkpatrick for her virulently partisan foreign policy keynote speech at the Republican convention.

Then Vice President George Bush moved into contention with his spurious claim that Walter Mondale and Geraldine Ferraro were going around saying that the Marines in Lebanon had "died in shame." But Bush, as an elected official, at least has a license to practice partisanship. Sound tradition dictates that foreign-policy-makers appointed by the president do not.

So Kirkpatrick was out front until last week. Then Sen. Jesse Helms (R-N.C.) proudly announced he had the support, in his bitter race for reelection against Gov. James Hunt, of 22 U.S. ambassadors and one former ambassador who were all political appointees of President Reagan. (Later the ambassador to Mexico, John A. Gavin, said his message to Helms was only a birthday greeting, and in no way constituted an endorsement.)

To appreciate the unseemliness, not to say squalor, of this intervention in a U.S. Senate race by practicing U.S. diplomats requires some sense of the role Helms plays as a member of the Senate Foreign Relations Committee. But first, a careful look at the language of his announcement of the ambassadors' "historic" endorsement:

"The ambassadors are all appointees of President Reagan and are on the front line of the president's foreign policy. The endorsements are a tribute to Sen. Helms' strong leadership role in strengthening America's foreign policy."

Now if that says anything, it says that those ambassadors believe Helms to be a stalwart supporter of the Reagan administration's foreign policy. And it sends that message to the people as well as the leaders of the nations and organizations to which the ambassadors are directed to convey U.S. policy.

Helms' list of active-duty ambassadors included those accredited to France, South Korea, NATO, the Organization of American States and a number of important countries in South America, Central America and the Caribbean. The message sent to Latin America has particular weight. Helms is chairman of the Western Hemisphere subcommittee of the Foreign Relations Committee.

In that capacity, he has done his irresponsible best to sabotage the Reagan administration's appointees to Latin American ambassadorships and high-level State Department jobs on the grounds that they were insufficiently reactionary. The notion that he is, or has been, on the "front line" of the president's foreign policy is nonsense, given Helms's open support of Argentina in the Falklands war and his public display of friendship with Roberto D'Aubuisson, the right- wing leader with connections to El Salvador's death squads.

But message-scrambling is not the worst part of it. Political appointees are free to play politics in a way that career professionals would not be, even if they were not forbidden to do so by the law. The worst part is that they feel so free to violate the spirit of the law. What we are witnessing is yet one more example of a more generalized licentiousness -- an acute absence of any sense of rightness by those whom we are accustomed to think of as being in charge. You need look no further than to the State Department's limp response.

By way of the tiniest wrist-slap, a statement, bearing nobody's name as the voice of authority, said, "The Department of State is not involved in any political campaign. Secretary Shultz has stressed to our ambassadors that they are full-time federal employees whose primary task is the timely and successful completion of their official duties."

The statement added that this conforms with White House policy and with longstanding tradition "which has discouraged ambassadors from participation in partisan political campaigns." Obviously, in this case, it didn't. It went on to say that the active ambassadors on Helms's list have been "reminded" of their "first responsibility" to "the nation and the execution of foreign policy."

There will be, out of this episode, new pressure to cut back the number of political appointments to ambassadorships. But even though the Reagan administration has probably overdone it, the practice is well-established. It is unlikely to be circumscribed by quota systems or other restraints; the numbers are not the point.

The real point has to do with the spirit behind the practice: the quality of the appointees; their professional standards; the cast of mind they bring to the job. In North Carolina, 21 politically appointed Reagan ambassadors have just shown us all we needed to know about their cast of mind.