The 1984 election should prove to us, once and for all, that while church may be kept separate from state, religion and politics cannot be sealed off in exclusive compartments.
Indeed, if you take the long view on American history, it may be argued that the very decision to separate church and state depended upon the interplay that occurs when theologians think about politics and politicians think about theology.
In practice, the presence of religion in the politics of 1984 was not always edifying. A certain shrillness characterized both the supporters and the detractors of the Rev. Jerry Falwell. The conscience-wrestling between New York Gov. Mario Cuomo and his bishop turned out to be a bit of a sideshow. And the rather hasty bumper-sticker considerations of ''right to life'' issues, school prayer, and Armageddon did little to elevate the campaign.
But the fact that religion, in whatever form, was not regarded as irrelevant to political discussions constituted a matter of significance. It was as if, in a campaign that often seemed to be dominated by the superficialities of public-opinion polls and TV ''image,'' everybody hungered for substance - something that went beyond the cult of personality or the strategies of media blitz.
At a conference sponsored by both Harvard Divinity School and the John F. Kennedy School of Government, the theologian Harvey Cox sensibly accepted the inevitable connection between religion and politics: ''The linking of religious discourse to public policy is important (1) because our politics needs it, (2) because our faith requires it, and (3) because our people want it.''
The dialogue between religion and politics is not, of course, limited to a presidential campaign, nor is it just an American phenomenon. The crossover seems to coincide with a sense of helplessness in the facts of history. Thus the threat of nuclear war today drives even humanists to fall back upon religious terminology - Apocalypse, Doomsday, etc. - in order to gauge the moral magnitude of the risk.
Life might be easier at times if religion and politics could be separated. The assassination of Indira Gandhi, the cruel excesses of Islam fundamentalists in Iran, the terrorism in Ireland - all measure the furious passions that can result when religion and politics make a fanatical mix.
But on the other hand, with no religion present, politics tends to become men playing at being God, making secular religions out of fascism, communism, and all the other isms.
The religious man or woman may long to transcend history, or withdraw from it. The political man or woman may pray, as the cynical joke goes, ''Our Father, Who art in heaven, stay there.'' But the need on both sides to make a connection between one's beliefs and one's daily life is irresistible.
Alas, when theologians muddle into politics and politicians muddle into theology, things can get crude. The simplicities of far right evangelists at home are matched by far left ''liberation'' theologians in Latin America, attempting to reconcile Marxism and the New Testament.
At worst, the temptation is to play the game, ''If Jesus were alive today, what party would he belong to?''
But at best, the leaven of religion in politics can make the exercise of power gentler, and the vision of justice more sensitive. At the sight of the starving, it should prompt us to care, without calculation. In the presence of the enemy, it should remind us to see also the children of God.
Rather than making us more self-righteous, the interplay of religion with politics ought to make us less self-righteous, after the model of Abraham Lincoln, who, Dr. Cox suggests, may have been ''the most profoundly religious President we have ever had.''
During the hatred and violence of 1862, Lincoln addressed himself directly to the subject of religion and politics. ''In the present Civil War,'' he found the courage and wisdom to write, ''it is quite possible that God's purpose is something different than the purpose of either party.''
This is not the last word on religion, but it may well be the last word on politics.