One purpose of the US election campaign should be to clarify and define the nation's course in foreign policy for the period ahead. It is necessary as a basis for working effectively with allies and friendly nations, and for constraining adversaries - in short for ensuring that our actions and power advance our security and well-being.
That the US has not had such a policy for nearly two decades is a fact. Since the late 1960s, our course has been erratic, lacking a stable conception of our national interests and of the appropriate means for pursuing them. Our oscillations have confounded both allies and adversaries, and gravely eroded our influence with both. Allies have found us unpredictable as a collaborator; adversaries saw our conduct as a sign of weakness. Today there is no solid consensus on how to deal with the Soviet Union, on defense spending and strategy , on guides for intervention abroad, or on major requirements for economic interdependence. The causes are many and varied. Vietnam and the overselling of detente undermined the postwar consensus. But other contributing factors included changes in the political system, Congress, the news media, and communications, as shown by a recent study, ''Our Own Worst Enemy,'' by Destler, Gelb, and Lake. Foreign policy has become more political, more ideological, and subject to wider swings.
The debate has often been partisan, but the parties have gone through their own gyrations. That was reflected in the oratory at the recent political convention. The Republican Party of today would like to forget Richard Nixon's detente and ''new structure of peace'' with the USSR. It is uncomfortable with the centrist moderation of Dwight Eisenhower, who sought to restrain excessive defense spending and to explore ways to control arms and improve relations with the USSR. Harry Truman and John F. Kennedy are hailed as staunch patriots to attract disenchanted Democrats. Likewise, the Democrats would prefer to ignore Lyndon B. Johnson and Vietnam and Jimmy Carter and his vacillations regarding the Soviets and defense.
Judging by the signs thus far, the hope for reasoned discussion of our future course looks dim. Apparently the Reagan campaign will rely mainly on tying Walter Mondale to former President Carter and on emotional appeals to patriotism and nationalism. The President, Ambassador Jeane Kirkpatrick, and others sounded these themes at the convention. America can once again be proud. Any criticism of Ronald Reagan's policies shows a proclivity to ''blame America first.'' That, of course, is nonsense. Critics of the Lebanon fiasco are not blaming America, but the confused goal and inept execution of the administration. Objection to an ill-defined defense strategy and to reluctance to explore arms control does not reflect ''softness'' on the Soviet threat but hardheaded realism. Right or wrong , Grenada is hardly a major triumph.
Yet in fostering informed discussion, the performance of Mr. Mondale and the Democrats has not been very impressive, either. Making the nuclear freeze the litmus test of arms control (as Mondale did in the primaries) may be popular, but it defaults on the duty to educate on this complex subject. The freeze may be an effective bludgeon, but it is hardly the best force toward useful arms control. Aside from the inherent difficulties in negotiation and verification, it could impede measures to improve stability by adapting weapons systems - as was the aim of the build-down proposal derided by Mondale. The anti-interventionist platform plank is also more doctrinaire than realistic. And the total embrace of Israel, and of Jerusalem as its capital, subordinates US interests in the Middle East to solicitation of ethnic votes. Similarly, ''domestic content'' requirements for cars appeal to auto workers, but are hardly good guides for economic policy.
Doubtless the advisers consider these the routes to political success. They may of course be right. But if they are, it is difficult to imagine how the US will return to a centrist, coherent foreign policy anytime soon. They may well be wrong. The electorate may be more sensible than politicians assume, and respond to honesty and candor in discussing the complexity and dilemmas of foreign policy and the US role in the world.
Actually, Mondale has already taken the gamble that this is so in domestic affairs by telling the truth about the inevitability of increasing tax revenues to cope with the massive budget deficits ahead. He might be wise to take the same approach on foreign affairs. If he did so, he might be able to force serious debate of the critical choices about East-West relations, defense and arms control, international economic policy, and relations with developing nations. Otherwise we seem fated for a campaign of slogans and simplistic claims and charges that will enlighten noone.