IT SEEMS a fateful irony that the first term of Jimmy Carter's presidency is coming to a climax, in the hostage crisis, with a test not so much of policy as of character. Here after all is a man who, even after he finally found it convenient to point to his experience and supposed competence in governing, has never stopped stressing the personal integrity and moral courage he claimed to be bringing to his high duties from the start. Yet it is precisely these personal qualities that are widely questioned -- and in respect to no issue as much as deservedly as to the hostages. Repeatedly in the past year Mr. Carter has handled the issue in a way that raised suspicions that he had an excessive concern for its impact on his political fortunes. As he enters the election countdown, also conceivably the hostage countdown, Mr. Carter is under a heavy burden to demonstrate that to get the hostages, and thereby presumably to promote his reelection, he will not give away the store.

It can be argued that Mr. Carter should delay any quest for the hostages until after the election, so as to avoid giving the Iranians the negotiating advantage they would seem to hold over him by virtue of his eagerness to bring home the captives by Nov. 4. But so few and slight have been the negotiating openings so far, and so utterly unpredictable are the opportunities that may open in the future, that it would be rash for any president to pass by what he thought was a good opportunity now. Perhaps Mr. Carter, lame duck or reelected, or Mr. Reagan will be in a stronger negotiating position after the election -- without a political need to produce quick results. But what kind of a position, or mood, will the Iranians be in? One can write different scenarios, but that is exactly the point: a flat decision to wait makes American policy excessively dependent on the volatility of the Iranian political scene.

With all due deference to the travail of the hostages, however, there must be limits on what an American president will "pay" for them -- whenever the bill comes in. He cannot make promises, say, in the matter of frozen Iranian assets, American financial claims or Iran's demands for the late shah's property, that bend the American constitutional or judicial framework. He cannot make an "apology" that is untrue to the sense that we believe most Americans have that the American purpose in Iran over the decades has not been a hostile or malicious one. He cannot become, by providing arms either directly or through third parties while the fighting goes on, a military partner of the Khomeini regime.

This is tricky. Iraq, not without provocation, did send its forces into Iran, and the war is being waged on Iranian soil: it is not as though Iranian troops were in Iraq. Yet the United States cannot ignore its own (and its allies') oil-, friendship- and strategy-connected relations, with Iraq; and it cannot ignore its relations with Iraq's Arab supporters, particularly Saudi Arabia -- and even with some of Iraq's Arab rivals, such as Egypt, which is dismayed to see the United States looking "soft" on Iran, whose chief support is Egypt's rival, Libya.

This is why it is so important for the United States, in the company of other nations, to be pursuing a cease-fire and negotiation in the Iran-Iraq war, at the same time that the hostage minuet proceeds. A cease-fire lets the United States help, honorably, to provide Iran a usable return, and it presumably would take the curse off a partial resumption of U.S.-Iran ties as far as Iraq is concerned.

The drama is unfolding in the dark of discretion and the fog of confusion, and so it is hard to judge particulars. For Jimmy Carter, however, the challenge is whether he can separate sufficiently his electoral interest and the national interest, where they may in fact not be the same, or even be in contradiction. Does he have the inner strength to pass up a politically tempting deal if the terms are wrong -- even if they would not become known for some time? Does he accept that, beyond the terms, the resolution of this problem must leave the United States better placed to deter or to cope with similar problems that may arise elsewhere later? It is a test of character that the president faces, unquestionably the most demanding to have confronted him so far.