WHEN Corazon Aquino's ``people power'' toppled Philippine President Ferdinand Marcos last year, even the normally stolid Secretary of State George Shultz was moved. Announcing Mrs. Aquino's victory, he described it at the White House as ``one of the most stirring and courageous examples of the democratic process in modern history.''
Just weeks earlier, Reagan administration officials had watched and prodded a revolution in another part of the globe, as Jean-Claude Duvalier fled Haiti for comfortable exile in France.
In both the Philippines and Haiti, the United States was faced with volatile, fast-changing situations in strategically important areas that required deft handling if US interests were to be preserved. Using lessons learned in 1979, when friendly governments in Iran and Nicaragua were swept away by radical revolutions, the administration responded with flexibility, cutting ties to pro-US dictators Marcos and Duvalier.
But success in the Philippines may not make dealing with political change elsewhere easier. As friendly regimes in countries like Chile, Pakistan, and South Korea face mounting pressures for democratic reform, learning how to prod change without jeopardizing political stability is likely to remain the most exacting task of American diplomacy.
``The bottom line is that we have to remain true to our own democratic principles,'' says Richard Kessler, a Philippine specialist at the Washington-based Carnegie Endowment for International Peace. ``But how aggressively we pursue them depends on the situation. If we push too hard, we risk destabilizing a friendly regime. If we don't push hard enough, events will take over, leading to an outcome hostile to US interests.''
Knowing just when and how hard to ``push'' friendly governments toward democratic reform is an old problem in American statecraft. But as the events of 1979 in Iran and Nicaragua demonstrated, the stakes involved in such decisions are higher than ever before.
Whether the US could have altered the outcome of either revolution remains a point of disagreement between liberals and conservatives.
Conservatives say stronger US backing might have saved Shah Muhammad Reza Pahlavi of Iran and President Anastasio Somoza Debayle of Nicaragua, pillars of US interests in the critical Middle East and Central America regions.
Exponents of this view, led by former United Nations Ambassador Jeane Kirkpatrick, say the US undermined trusted allies by putting human rights concerns ahead of strategic interests. The result has been regimes - Ayatollah Ruhollah Khomeini's in Iran and Daniel Ortega Saavedra's Marxist government in Nicaragua - that have eroded longstanding US regional-security arrangements.
ACCORDING to the ``Kirkpatrick doctrine,'' the US should be more prudent in pressing human rights reforms in ``authoritarian'' countries sympathetic to US interests - especially where the alternative to the government comes from the extreme left - than it is in dealing with ``totalitarian'' countries ruled by communist governments.
``The basic point is that an authoritarian regime can be changed by internal forces,'' says James Hackett, editor of the National Security Record published by the conservative Heritage Foundation. ``Totalitarian regimes can't.''
Proponents of the Kirkpatrick doctrine cite examples like Uruguay, Argentina, and Peru, where military dictatorships have given way to democratically elected civilian governments.
Many liberals disagree. They say more US pressure for human rights reforms - not less - was needed to strengthen the hand of moderate elements in both Iran and Nicaragua. Liberals say that as it was, by looking the other way as pro-US regimes tortured opponents, the US nurtured the very environment that produced the radical regimes, with their strong anti-American orientation.
A fervent anticommunist, President Reagan himself has hewed to a policy, known as the Reagan Doctrine, of supporting ``freedom fighters'' seeking to overthrow communist governments.
But impressed by the peaceful transfer of power in the Philippines, the President's views appear to have moderated somewhat. Last March, Mr. Reagan hinted the US would be more aggressive in prodding friends as well as adversaries on the issue of human rights.
`THE American people believe in human rights and oppose tyranny in whatever form, whether of the left or right,'' Reagan told Congress.
This ``small but important course correction,'' says one State Department source, has been most visible in Chile, where US Embassy officials now meet regularly with opposition groups. The US has pressured Gen. Augusto Pinochet Ugarte, Chile's right-wing military leader, to hold free elections in 1989, using threats to veto international loans to Chile as leverage.
The dilemmas and risks involved in responding to political change are epitomized in the case of Nicaragua.
Motivated by concern over the safety of US investments and the security of the Panama Canal - and more recently, by the desire to contain the spread of communism - successive US administrations have sought to insulate Central America from outbreaks of political instability.
US Marines were used to preserve order in Nicaragua between 1912 and 1933. Since then, the US has relied on the unwavering pro-US sympathies of the 46-year family dynasty founded by Anastasio Somoza Garc'ia.
General Somoza and his sons quickly acquired, then abused, vast amounts of political and economic power. As early as 1949, the State Department reported that the Nicaraguan people were enduring ``repression, widespread illiteracy, intimidation, and poverty.''
But the US continued to back the Somozas with political support, weapons, and economic aid, concerned that the alternative to Nicaragua's pro-US government would be a regime hostile to American interests in the Caribbean. The Somozas returned the favor with diplomatic and military support for the US-backed 1954 coup in Guatemala and the 1961 Bay of Pigs invasion against Fidel Castro's Cuba.
Starting in 1977, the Carter administration tried to use Nicaragua as a test case for its new human rights policy. Under US pressure, President Somoza reluctantly reined in his personal constabulary, the National Guard, lifted a 33-month state of siege, and restored Nicaragua's free press.
By then it was too late. With prospects for free elections as remote as ever, moderate business leaders, clergy, and students joined the struggle, led by leftist Sandinista revolutionaries, to overthrow Somoza.
``The Somozas controlled elections to the point that there was no other way to attain power except through revolution,'' says Walter LaFeber, a Cornell University historian.
Already in electoral trouble at home and facing the possibility of another Cuban-style Marxist regime in the region, President Carter made last-minute attempts to find a workable moderate alternative to both Somoza and the Sandinistas. But the effort merely exacerbated the suspicions of the victorious Sandinistas, who finally took control of Nicaragua in July 1979.
``We end up supporting the status quo, making pressures for change build up till they finally explode,'' says Thomas Walker, an Ohio University political scientist, referring to the US experience in Nicaragua. ``If the United States had not so stubbornly backed Somoza, change could have come more easily and with less violence.''
``The point is that we've got to learn to live with the natural process of change,'' adds Professor Walker, an expert on Nicaragua. ``Even if change doesn't immediately appear to be in our interest, we can find ways of dealing with it. We've learned in Iran and Nicaragua that when we try to thwart change we're only inviting trouble.''
In the case of Iran, the ability of the US to cope with political change was hampered by a major intelligence failure that obscured the growth of political opposition to the Shah. Like the Somozas, the Shah was a longtime friend, indebted to Washington for the Central Intelligence Agency's help in restoring him to power after a 1954 leftist coup.
Following Britain's decision to withdraw from positions ``east of Suez'' by the end of 1971, the US moved to fill the power vacuum in the Mideast and the Persian Gulf, establishing Iran as one of the pillars of US policy in the region.
USING vast amounts of US military aid, the US built Iran into the dominant regional power. Critics of US policy later complained of a reverse dependency, with the US eventually needing Iran more than Iran needed the US.
Unfortunately the Shah - also like the Somozas - ruled by repressive means.
By the 1970s, writes Gary Sick, a former National Security Council official and an Iran expert, ``the use of torture and political persecution had become commonplace'' in Iran.
Meanwhile, rapid economic modernization alienated the country's Muslim majority. Fueled by memories of US intervention in 1954 and by continuing US support for the Shah's repressive regime, radical Muslim opposition to the Shah turned violently anti-American.
Once again the clock ran out during the Carter administration. And once again news of an impending change of power produced divided councils within the US government.
Following reports that the Shah might abdicate, State Department officials pressed for a transitional government led by opposition moderates. National-security adviser Zbigniew Brzezinski prodded Mr. Carter to stick with the Shah.
Last-minute confusion was compounded by the Shah's own indecision and by the absence of reliable intelligence on the breadth and strength of domestic opposition to the Shah's rule.
In the end, the debate in Washington was overtaken by events. The Shah - who US officials learned only later was seriously ill - was forced out and soon died in exile. In Iran, the new regime of the ayatollahs pledged militant opposition to the US ``Satan'' and its moderate Arab allies in the Middle East.
Defenders of Mr. Carter say blaming 11th-hour indecision for the events of 1979 may be unfair. The radical anti-American cast of successor regimes in Nicaragua and Iran, they say, reflects the failure of decades, not months, of US foreign policy.
Whatever the case, managing political change in the future may be more successful thanks to lessons learned in 1979 - and in 1986, when the US response to revolution in the Philippines produced a major diplomatic success.
The peaceful transition to democratic rule that ended the 20-year regime of Mr. Marcos may not provide an exact model for similar revolutions elsewhere.
There are limits to what the US can do to influence the course of political change in other countries, diplomatic observers caution. But in dealing with places like Chile and South Korea in the future, the Philippine example of timely pressure, discreetly applied, may suggest the best approach to protecting US interests abroad.