Detective Hercule Poirot, the Agatha Christie hero, used to say about such things: "There are too many coincidences here for it to be a coincidence." You don't have to be a detective to notice the coincidence that all the prime ministers who embark on diplomatic steps involving concessions reach their goal without public, parliamentary, party or moral legitimization.

That is what happened to Yitzhak Rabin in Oslo, Ehud Barak at Camp David and Ariel Sharon in the disengagement. That is what is happening to Ehud Olmert on his way to the Annapolis conference. Men in a trap, which they helped to set for themselves.

It is hard to assume that this is only a coincidence, so we should seek an explanation for the phenomenon. An inevitable explanation is that Israeli prime ministers chronically lack legitimacy. The public does not actively recognize representative democracy and rejects the leader's right to adapt his actions to a changing reality.

This explanation could have sufficed had it been valid in war as in peace. But war actually enjoys absolute legitimization ahead of time (like the initial sweeping support for the Second Lebanon War), and loses it after the fact, according to the results. A failed war becomes an illegitimate war. This means we have to return to our basic assumption that any effort to promote an agreement, not to mention peace, becomes an illegitimate act.

But the denial of legitimacy is not only a distortion by a public that does not understand the rules of democracy. Prime ministers, one after another, have helped undermine the institutions of democracy while showing contempt for its spirit.

In the collective memory, will MK Alex Goldfarb serve as an example for cheapening the process, as someone who sold his right-wing soul to support Rabin's Oslo 2, in return for the job of deputy minister? Oslo 2 did in fact pass in the Knesset by a bare majority, but Rabin did not rehabilitate his moves' legitimacy.

Barak went to Camp David not only after making himself an object of hatred among most of his supporters, but after he had already lost his parliamentary majority.

This negligible fact not only didn't disturb the prime minister at the time, it led him to declare openly that he intended to bypass the Knesset. The guardians of democracy, who are sensitive to every blow to its foundations by the right, remained silent. There were even some who explained that it is permissible to bend democracy for the sake of peace.

Sharon, against whom investigations were already pending, undermined democracy for the sake of the disengagement, after totally ignoring the results of a referendum among registered Likud members, which he himself had initiated. "I received the results of the Likud members' referendum with sorrow," he said when the results became known. He soon succeeded in overcoming his sorrow and continued to implement the disengagement plan.

That does not mean that Oslo 2, the attempt to reach an agreement at Camp David and the disengagement were undesirable acts; on the contrary.

Nevertheless, there is a lesson to be learned here: An effort must be invested in guaranteeing legitimacy, just as it is invested in the diplomatic process itself. The ease of waiving this condition contributes to the tragic insolubility of the conflict.

Olmert on his way to Annapolis represents another aspect of the problem. He has an impressive parliamentary majority, but he lacks moral legitimacy. The investigations pending against him erase the moral basis of his leadership. Were it not a matter of human lives, it would be funny to hear the Israeli claim that "Abu Mazen cannot provide the goods" because he lacks a mandate from half his nation. Olmert has a mandate, but this advantage will not help him in light of his moral weakness.

We can only hope for a leader who will have both a plan and mandate and the moral authority to implement them. Even so, there will be people on the right who try to cause any agreement to fail. But at least it will be more difficult for them to do so.