This summer I read Gore Vidal's "Lincoln" -- more of an essay, really, than a novel. Vidal sticks to the facts about Abraham Lincoln, incorporating actual dialogue taken from historic journals to create a Lincoln who, Republican though he was, would have been booted out of the GOP convention. By Ronald Reagan's standards, Honest Abe was insufficiently religious.

In fact, Lincoln had an aversion to even mentioning the Almighty in his speeches, and when on occasion he did so, members of his Cabinet -- some of whom were deeply religious -- were both stunned and grateful.

I am hardly a Lincoln scholar, and so I cannot tell you if Lincoln was a religious skeptic or whether he held to the now-quaint view that religion is a deeply personal matter, much too serious and consequential to be abused for political reasons. He recognized, after all, that both the South and the North thought they had God on their side and that the Bible itself was used by both abolitionists and slaveholders to justify their conflicting positions.

Contrast Lincoln with the current occupant of the White House, Ronald Reagan. Here is a man who punctuates many of his speeches with references to the deity, who has reduced Him to the level of a Cabinet officer, made Him a cheerleader for the GOP and considers Him a contributor to his reelection effort. In the person of Sen. Paul Laxalt, the president has appealed to fundamentalist ministers to aid his campaign, even though he must know that if the ministers got their way Laxalt's state of Nevada, best known for gambling and divorce, would revert to desert.

I don't know what Lincoln would have thought of all this. I guess he would have been appalled. But the historical example of Lincoln suggests that a political leader's religiosity, especially one worn on the sleeve, tells you absolutely nothing about him. Lincoln, for instance, was clearly loath to invoke the deity and almost never went to church. Yet he was not only a great president but a great man.

On the other hand, Jimmy Carter, whose religious commitment was absolute, was hardly a great president and just an ordinary man. It hardly mattered to most people that Carter was a good Christian when at the same time the only thing zooming toward heaven was the prime rate. In such straits, they would have preferred Richard Nixon -- a man whose God is pragmatism.

The point is that a person's religious commitment tells you almost noth about that person. In fact, when it comes to safeguarding civil liberties and ensuring progressive and fair social policies, I would rather take my chances with your average atheist than, say, the Rev. Jerry Falwell. I grant you he is religious. But so, too, is the Ayatollah. It hardly matters to a poor, devoutly Christian American that the president who has made his life harder is also devoutly Christian -- or says he is. Religion is not what counts; politics is.

What's true for Reagan is true for all politicians. It hardly matters to me that Walter Mondale seems now to attend church with a vengeance and that Geraldine Ferraro does the same. And New York Gov. Mario Cuomo is no more or no less right in his political positions because he is a devout man. What matters -- the only thing that matters -- are the political positions they take. As they say in the Army, they can pray on their own time.

But if you can read the mind of the long-dead Lincoln, he recognized that religion can have a singular political impact. It can divide.

Lincoln was intent on unification, but that should be the goal of all presidents. When Reagan appeals to religion, he cites the one thing that divides us -- that makes us not Americans, not even Republicans and Democrats, but this or that religion or sect. It separates believers from non- believers, Christians from Jews, the born-once from the born-twice, and suggests that some sort of religious consensus can be reached at the polls -- a sheer impossibility in the multi-ethnic, multi-religious nation.

The president charges ahead anyway, injecting religion where it does not belong, excluding when he should be including. He has made the party of Lincoln into one that's inhospitable to the very essence of Lincoln himself, turning the deity into a party hack. That is the ultimate conceit. Ronald Reagan may or may not be a Christian, but when it comes to humility this much is certain: he is no Lincoln.