The latest storm over Cuba provides a textbook study in the mismanagement of foreign policy. But far more than abundant goofs are involved. For all the goofs lead back to a common policy -- the policy of trying to appease the Third World.

The blunders became vividly apparent with the surfacing of the present Cuban problem. On Aug. 30, Sen. Frank Church of Idaho was told about the discovery of a Russian combat unit. He announced the fact the next day, and demanded the unit be removed.

For four more days, various public persons echoed those views. But it was only on Sept. 5 that the administration began high-level deliberations on what to do with the Russian unit. Thus the issue was allowed to kick around publicly for a full week before the administration even began to determine its policy line.

The White House claims that Church was given advance notice of the combat unit only because it feared word was going to leak anyway. But even if he tried, which is not clear, the official who alerted the senator lacked the weight to keep him silent -- a first goof. Secretary of State Cyrus Vance did not persuade the senator it was important to stay mum -- a second goof. President Carter refused to take calls from Church -- a third goof.

The reason leaks were feared is that word of the discovery had spread widely within the intelligence community, which is not happy with the Carter administration. But the Carter administration had plenty of time to tighten its hold in the intelligence take from Cuba. It didn't -- another goof.

To sweeten the intelligence community, Vance spoke of the discovery in terms that made it seem the combat unit may have been in Cuba at least since 1976 and perhaps since the 1960s. That way, any charges of failure would be softened.

But in stroking intelligence officers, the secretary implicitly planted the suspicion that the dirty deed was done by the Russians while Gerald Ford, or Richard Nixon, was on the watch. With blame being directed at them, Republicans have not exactly been keen to help the administration.

As a matter of fact, something changed the nature of the Soviet presence in Cuba in an important way without American intelligence officers knowing about it and passing it on to higher authority. The reason for that failure is clear. Intelligence officers are sellers who respond to their customers. When a president wants information on Cuba, it is forthcoming. When he doesn't, he doesn't get it.

But the Carter administration didn't want intelligence about Cuba. It didn't even act on what came its way. Thus the secretary of state and the secretary of defense roundly denied the assertion when Sen. Richard Stone, on July 17, first claimed there was a Soviet combat unit in Cuba. Nor was there a serious reaction from the administration to earlier word that MiG fighters, sometimes with Russian pilots, were participating in the air defense of Cuba.

Nor to alarms about Cuban troops in Ethiopia and Yemen. Nor to the possibility that Cubans might be fostering, or at least turning to advantage, the radical movements taking over Nicaragua and other countries in Central America.

Why? Because a major theme of the administration has been the cultivation of radical, Third World countries. It embraced the policy of radical blacks for southern Africa. It bought the program of radical Arabs for a "comprehensive settlement" in the Middle East. It sought publicly to knit up ties with Vietnam -- not to mention Cuba.

In fact, the Third World countries have taken advantage of the administration. They have hit, and continue to hit, this country where it lives -- in the price of oil. They have sided with Russia -- most recently at the Havana conference of non-aligned countries -- in deriding American security interests in Europe, the Middle East and Asia.

The Soviet combat unit in Cuba is only one fruit of the policy of appeasing the Third World. That its discovery puts SALT in jeopardy and ditches the hope of reaching a consensus on defense spending may seem unfair. But it is not surprising. It is the cost that an administration pays for blindly following a dumb policy.