IN PAST EFFORTS of the United States to negotiate the release of the hostages in Iran, the difficulty has been that at the last moment the revoluntionary elements have abruptly withdrawn the authority of those with whom the United States was dealing. This has led the Carter administration sadly to the belief that a critical obstacle -- perhaps the criticial obstacle -- was the lack of a center of authority in Tehran capable of negotiating the terms of the hostages' release and making the bargain stick. Only after the chaos of the revolution yielded to a power structure acceptable to all the key Iranian players, it has been felt, could the United States hope to find a reliable negotiating partner.

Such a structure seems now to be coming into place. Ayatollah Khomeini has always had the power to free the hostages, but the parliament, the body to which he chose to assign responsibility for them, has now been elected and organized. It is becoming seized of the issue: its foreign affairs commission has proposed to the parent body a set of demands to be made on the United States. The militants who hold the hostages say the matter is in the parliament's hands.

Given the obscurities in Iran, it is foolish to try to predict how negotiations may unfold. It is at least conceivable that the new Iranian power structure, dominated as it seems to be by Islamic fundamentalists, may decide that the revolution needs the tensions generated by the holding of the hostages more than the relaxation available by releasing them. It is worth cautiously noting, however, that the Iranian parliament's opening bargaining position, are somewhat toned down from demands made in the past, and there is, of course, also the fact that the former shah is now dead. To ask for the physical return of the shah, as the terrorists regularly asked while he was alive, was from an American viewpoint unthinkable.

The State Department acknowledged the turn in Tehran by formally addressing the Iranian government on the hostage issue for the first time since the failed American rescue mission last April. This gesture of taking the new government seriously was well timed. There can be little doubt, however, that many Iranians fear the United States may still somehow use its force or wile to humiliate them in the matter of the hostages -- and that other Iranians play on these fears. This not only puts a difficult burden on American diplomacy. It also imposes on the presidential candidates an extra burden: to conduct any campaign discussion of Iran in ways that will not make the negotiations any more difficult than they are bound to be anyway.