WHAT IS one to make of Sen. Edward Kennedy's visit to South Africa? Certainly it was a striking media event, one coinciding with and reinforcing the new interest of the American public in apartheid. The senator drew on the recollection of his late brother Robert's tour 18 years ago. He sought out the scenes most expressive of white oppression of the black majority and presented himself as a new recruit to the struggle of South African blacks for dignity and equality. It is a struggle, he said, that puts him in opposition to the Reagan administration's policy of "constructive engagement," which he finds morally and politically wanting.

Sen. Kennedy has something of his brother Robert's quality of being able to summon other people's deepest feelings to the surface. Thus did he elicit sharp protests from a minority of radical black nationalists who, far from receiving his extended hand, rebuffed him as an agent of the capitalist system they blame for their situation. It goes without saying that the official white establishment fully reciprocated his severe judgment of its policies and bona fides. More unexpectedly, some white liberals who are in opposition to their government also felt the senator was grandstanding and butting in.

We are faced here with a political dilemma that Americans have got to resolve if they are serious about converting the latest burst of anti-apartheid feeling into a helpful contribution toward change. It is good to have Americans seeing and understanding the wickedness of a system that condemns blacks to serfdom on grounds of their race. That some Africans are bitterly distrustful of would-be Samaritans is not surprising. But those who come to help should be sure they do not leave having made their own personal strivings and purposes the center of discussion. They should accept an obligation to indicate a strategy that actually has a chance to deliver some of the relief and benefit their intercession promises.

"Constructive engagement," with or without the quotes, has been the policy of successive American administrations at least since President John F. Kennedy. The constant has been to accompany pursuit of routine national interests with criticisms of apartheid; the variable has been the degree of feeling and frequency of these criticisms. Recently -- belatedly -- President Reagan came into line with other presidents, at least for the moment, by himself making a strong, public attack on apartheid. Still, it might profit the American debate if it were accepted that no administration, Democratic or Republican, liberal or conservative, has much dented events within South Africa in the past 25 years. Local forces are controlling, and the question is what further pressures or blandishments, mounted from outside, will make things better inside.