Spinning a globe in search of some happy legacy left to Ronald Reagan by Jimmy Carter, there are, alas, not many that the president-elect, given his stated view of the world, would joyfully accept.

Not the Panama Canal treaty, certainly; Reagan fought it tooth and nail. Not the Camp David "framework for peace"; Reagan talks vaguely of a return to the square one of United Nations Resolution 242. Not the "normalization" with China at Taiwan's expense.

But wait. There is one corner of the globe where things are looking up -- where recent events offer an opportunity for Reagan, as president, to reinforce a piece of Carter foreign policy under circumstances that nicely fit his own expressed preconceptions of how to deal with the rebellious Third World.

I have in mind the turbulent Caribbean region and the anticipated effect upon its politics, progress and general welfare of the election in the island nation of Jamaica, just one week before our own vote.

Under less than ideal conditions (sporadic gunfights and considerable bloodshed disrupted the campaigning right up to election day), Jamaicans overwhelmingly voted out of office the leftist, social democratic government of Prime Minister Michael N. Manley, close pal of Cuba's Fidel Castro and a loud voice in the world of the "non-aligned." The winner was Boston-born Edward P. G. Seaga, hostile to Castro, friendly to the United States.

It was a victory for competence over charisma, for the promise of thoughtful, innovative, middle-of-the-road approaches to almost intractable social and economic problems over the performance of what one U.S. official called "baloney ideology."

Administration officials do not presume to take credit for it. But the outcome does strongly confirm a conviction underlying U.S. policy in recent years. That is that there are strong moderate home-grown, nationalist impulses and identifiable moderate elements in almost all of the brand-new (and older) countries in a Caribbean basis made all the more critical to the United States by reason of simple proximity.

American diplomacy, the administration has argued, ought to be aimed at working quietly with the moderates (political leaders, businessmen, the clergy), serving as honest-broker in resolving the conflicts between the extremes of the right and the left, with the encouragement of generous economic aid.

In sharp contrast, Ronald Reagan more than once has expressed strong suspicious about the reliability of any supposed "moderate" elements and the wisdom of trying to work with them.

He has warned repeatedly of the threat of the Soviet presence in Cuba, of Castro's powerful, all-pervasive influence, of Caribbean "dominoes" falling, or about to fall.

What the Jamaica vote says to State Department experts and others is, as one of them puts it, that "the Cubans are not invincible; there is something left to the political process; that there are people down there who don't want radical solutions; that substance has a chance to triumph over rhetoric."

One Jamaican election isn't a bellweather, of course. But it does fit a pattern, over the past year and a half, of moderate victories over leftists in five other new, island mini-states in the area: St. Kitts-Nevis, St. Vincent, Antigua, Dominica, St. Lucia. This hardly confirms the impression one often gets of a slow, irreversible slide to Castroism.

"As closely identified as he was to Manley," says one top administration official, "this has to be a setback for Fidel."

The immediate U.S. response has been to begin cranking up various forms of direct or indirect economic support for the new Seaga government in Kingston. One move would be to revive an International Monetary Fund loan for Jamaica. American allies, already joined with the United States in a Caribbean Consultative group that includes Canada, Britain, Venezuela and Japan, will be urged to pitch in. There's hope for increased private investment from businesses turned off by Manley's policies and the resulting economic chaos.

But any sustained help will be up to a Reagan administration. In his recent televised foreign policy pronouncement, he promised a program of "intensive economic development with cooperating countries in the Caribbean" and indicated considerably more sympathy and understanding for their plight than he had in the past. Many of them, he said, were granted independence and "promptly forgotten. In their natural resentment, some have turned to extremist models, fertile ground for Cuban meddling. Our programs will assist them both financially and technically. . . ."

If Reagan should move quickly to apply those programs to Jamaica, the experience could be as instructive to his new administration as it would be constructive to Jamaica's new government.