Of all the myths of American power nourished in the halcyon days of American "empire," none grew taller than the conviction that the United States could and did cut down uppity foreign regimes at will. The wings of the CIA have been clipped in recent years and presidents are slower to authorize, and legislators to approve, covert operation. But the myth linger on. Especially in the Third World and on the American left, belief remains widespread in the CIA's bent for "destabilization." The term entered the political lexicon to describe the campaign against Chile's Salvador Allende, killed in a coup in 1973

Take, now, Jamacia. Allegations of a CIA destabilization effort have become a standard part of the political dialogue on the troubled Caribbean island, It is stated as though it needs no further proving that the Ford administration tried, through it failed, to block the reelection of Michael Manley in 1976.

The Carter administration's open sympathey for Manley's program of "democratic socialism" has made it hard to claim that Jimmy Carter is trying to block Manley's current reelection campaign. Manlely has sometimes been willing to go on the record and take Carter off the hook in this Regard -- and sometimes not.

But a bizarre theory has sprouted according to which former CIA hands, rogue elements embittered perhaps by having lost their jobs, are still playing their old tricks, or are being manipulated by the Jamaican oppositon or American right-wingers, or something. Manley himself freely uses the loaded term "destabilization" to explain the difficulties besetting his country -- and his reelection campaign.

Why, it is asked, did the CIA Jamaica station chief, whose home was shot up at 2:30 a.m. one morning last month after an American anti-CIAnik exposed him, wait until the opening of normal business at 8:30 a.m. to inform the Jamacian police? Could it have been because the fellow had his own house shot up? For the record, I was unable to reach the man in question, and that a station chief had shot up his own house.

Why, it is further asked, has the United States suspended new aid projects if not in echo of Richard Nixon's anti-Allende directive to "make the economy scream"? The answer, I believe, falls short of a conspiracy. The aid people have been under congressional pressure mobilized by Sen. Richard Schweiker (R-Pa), who has long challenged Manley's socialistic pro-Cuba policies and his use of aid. Schweiker has further roiled the waters -- at the State Department, by the way, as in Jamaica -- by championing the expropriation claim of a Delaware businessman named John Rollins.

Why has the recent rate of private American investment on the island tailed off? Again, the answer, I think is innocent enough. Investors, seeing the turmoil and aware that a turning-point election is coming up, are pausing to see what comes next.

Manley fears a replay of Chile with himself in the role of Salvador Allende, he told me the other day while he was briefly in Washington. He sees himself being punished for his attempt to put Jamaica in the nonaligned column, with Cuba, in its economic policies and its international orientation. "We are trying to develop democratically but we are paying a bitch of a price," he said.

It is virtually an article of faith among American lefists that American "impreialism" is doing in brave, virtuous, socialist, Third World Jamaica. Sympathetic echoes of this view have been heard from the congressional Black Caucus -- Jamacia is mostly black.

But another explanation strikes me as more plausible. Manlely's bold attempt since 1972 to restructure the Jamaican economy has coincided with brutal upheavals in the world economy. Facing reelection now, Manley shrinks from telling his constituents -- whose expectations he, a formidable stump speaker, aroused -- that he is in some measure responsible for making Jamaica the only country in the world with declining growth for seven straight years.

Instead, the blame has been laid on the United States, or rather -- since the United States is popular in Jamacia and is the home of a million Jamaicans -- on the great shadowy institutions through which American power is often thought to be wielded in the Third World: the CIA and, on the economic side, the International Monetary Fund.

In short, Manley may have the best of both worlds. The power of the CIA is not, I think, arrayed against him. But the myth of the CIA provides a key element in his political strategy. He is David with a phantom Goliath.