Ethnic politics and foreign policy

President Reagan in his recent speech to Cuban-Americans in Florida has begun the quadrennial campaign appeal to the nation's politically important ethnic groups. He will undoubtedly repeat the ritual with other groups; his opponents will do the same.

This wooing of audiences of various national origins in the United States has become a significant part of the process of elections. There is little likelihood that this will change. No one, however - neither the President, his advisers, nor his opponents - should be blind to the effect of ethnic politics on a coherent foreign policy.

We are a nation of ethnic groups, each with its recollection of old traditions, symbols of a prior homeland. Appeals to such nostalgia are a common and harmless part of our political ritual.

The situation is different when the aim is to cultivate groups whose homeland is involved in a critical international issue. Approaches to such communities inevitably risk giving signals well beyond the confines of domestic politics.

Ethnic communities have their own set of objectives, their own agenda, created out of nostalgia for a lost land, hatred of a successor regime, or passion over an ancient quarrel, and motivated by a determination to enlist the US in their cause.

The supporters of Israel want a total US commitment to that country. The Greeks want us to adopt their wariness toward the Turks. Those from the ''captive nations'' of Eastern Europe want us to roll back the Soviet presence. The Cubans in Florida want us to overthrow Castro.

US administrations may agree with at least some of these ethnic objectives, but an official policy will take into account wider interests and the views of friends and allies abroad as well as the Congress and the public at home.

Speeches delivered on ethnic occasions may well reflect the more considered policy in their text, yet it is the setting and not the substance that becomes important. It is difficult for a president to speak with obvious sympathy to a group of anti-Castro Cubans, carrying placards and shouting ''Reagan, si, Castro , no'' without risking some degree of official identification with the bolder objectives of the community.

The more serious implication for US foreign policy is that the group's agenda may become the President's as well. Ethnic audiences, listening to a significant political leader, will hear what they want to hear. Expectations are inevitably raised that the power of the US will be used to help them realize their objectives. Other realities or limitations are lost in the euphoria of the setting. Commitments are assumed. Whether it be the US national will or not, the sympathy extended on such occasions creates the mood and substance of confrontation, whether with Arabs, or Soviets, or Cubans. They are listening, too.

A constant complaint by friends and allies observing our policy process is that we speak with many voices; it is difficult for them to know what US policies really are. We can refer them to the carefully considered statements that represent the culmination of a studied executive process and say, ''This is it.''

They are not blind to our customs, however. They will look also at the implications of statements made in appeals to particular groups in campaign settings. Professing that we do not intend to overthrow governments in Central America loses credibility in the face of a President's identification with those who have that as their central objective. The problem of ''multiple voices'' in the expression of our foreign policy is not confined to that of different spokespersons; our political process means that the same person can, in different expressions in different settings, contribute to the confusion.

There is a longer-term effect. When a group has delivered its vote for a successful incumbent or candidate, it then calls for the adoption of its policy agenda. In the case of an incumbent, the demands can come even before the vote. Every US administration has had to deal with the ''cashing of checks'' presented following appeals to an ethnic vote. The long months spent trying to balance that obligation with the realities of responsibility create only uncertainty and confusion. The president may, in the end, find that his own agenda is seriously altered by the conflicting claims and pressures of another.

In the incredibly difficult task of creating a coherent foreign policy for the US, administrations must give heed to the voices of the many concerned groups of national origins within the country. The balanced consideration of the interests of these groups is thrown seriously out of phase by the temptations and requirements of political campaigns. Competitive promises not only destroy bipartisanship but give conflicting impressions abroad.

There seems little chance that the ritual will end. We should not be surprised, however, when our friendly but skeptical critics abroad, seeking the truth about our policies, look beyond the carefully phrased official statements to the parochial expressions offered by our political leaders to ethnic audiences.