Miami -- THE CHAMPAGNE is on ice here. The Cuban community in exile is in no doubt that the aging Fidel Castro, erstwhile revolutionary guerrilla of the Sierra Maestra, scourge of John F. Kennedy, sower of discontent in the Andean peaks, tail-wagger of the Soviet Union and last surviving caudillo of Latin America, finally is in sight of his come-uppance.
No man is an island, not even in the lush and potentially self-sufficient Caribbean. Mr. Castro cannot survive without a financial and political mentor and protector in Moscow. His people may not be allowed to know much, but enough has seeped in for them to know Eastern Europe has changed and the Soviet Union is changing. Why, even in a Havana cinema, so it is reported, last year young people began to sing the song, ''This Man is Crazy, He Thinks He Rules the World.''
Yet the man in question seems as solid as ever. Mr. Castro is no Romanian Ceausescu. He has given the people tangible
improvements -- health care and a good education. Neither is he an East German Honecker; he's always kept a certain distance from Moscow and reserved room for maneuver. He constantly reminds the Cuban people that it was their home-grown revolution, their own boys and girls, not some heavy-footed ''liberating'' outsiders, that overthrew the Batista, run-the-country-like-you-run-a-casino regime.
He has charm, charisma, style and a lot of show, all things no communist in Europe ever had. More to the point, he is not yet economically and politically in so tight a corner that he need capitulate on someone else's terms.
Moscow is clearly winding down its economic subsidies. Yet it is counter-productive for Moscow simply to pull the plug: The sugar, nickel and citrus fruit it imports from Cuba without having to spend hard currency are of value.
Politically and militarily, too, Moscow finds at least a residual value in Havana. Not since 1974 has a nuclear-armed submarine has called on a Cuban port; yet on the island Moscow has a highly sophisticated eavesdropping complex that allows it to monitor American compliance with the various arms-control treaties.
But the point the hard-liners in Washington miss -- and no administration has been as unyielding toward Havana as George Bush's -- is that Mikhail Gorbachev does not want to be seen to throw in the towel on Cuba under U.S. pressure.
Mr. Gorbachev has been prepared to encourage Cuba to negotiate over Angola and to chivvy it to cut its arms supplies to Central America -- they now only go to the El Salvadoran guerrillas -- but he is not prepared to initiate Mr. Castro's overthrow.
The danger of blanket hostility toward Mr. Castro is that those who indulge in it are likely to miss the real signs of change. Uncompromising though Mr. Castro is, particularly on the question of political rights and civil liberties, he is not the same man as five years ago. It's a long time since he unleashed his revolutionary fervor on the South American mainland, and these countries rewarded him last year with the traditional Latin
American-held seat on the U.N. Security Council.
Likewise, he has pulled his troops out of Ethiopia and is now doing the same in Angola, although only after the Cuban army and air force had stalemated South Africa's crack units did South Africa take up Cuban compromise proposals that had been on the table for four years.
Mr. Castro is neither as inflexible as his rhetoric suggests, nor as single-minded as his opponents in Washington and Miami insist. Yet one thing has become clear over the 30 years of this intense adversarial relationship: The more hostile America is, the less he's interested in internal liberalization.
The Vaclav Havel-to-be of Cuba, Elizardo Sanchez, is the first to argue this. Now in prison, as he has been before, for human-rights agitation, Mr. Sanchez advises Washington to loosen its stranglehold. So do the Catholic bishops.
Washington should start by opening the phone lines and the fax -- remember the catalytic role they played in Beijing's Tiananmen Square. Next, let the mail and the clergy through and wait for the pope's visit next year to stir the waters. Open a hole in the economic embargo to allow in medicines, and at the same time send in study teams to see how Cuba got its infant mortality rate way below Washington D.C.'s.
Popular though Mr. Castro has been, no Marxist can survive in the 1990s unless his enemies in Miami and Washington keep on making the stupid mistake of continually resuscitating his nationalistic and revolutionary appeal.