Last Monday, in what seemed a supremely irrelevant vote at the time, Ariel Sharon, the leader of Israel's right-wing opposition Likud party, opposed a parliamentary bill which would formalise a blanket exemption from military service for ultra-Orthodox men who study Jewish texts full time.

Yesterday the five members of the ultra-Orthodox United Torah Judaism Party, who had strongly championed the bill and were pleased to see it pass its first reading despite Mr Sharon's opposition, punished the Likud leader by abstaining in a far more critical vote, a no-confidence motion in the government of the Prime Minister, Mr Ehud Barak.

By abstaining, these five ultra-Orthodox politicians helped ensure that Mr Barak's government did not fall. Had Mr Sharon voted differently last week, several analysts suggested yesterday, the dramatic splintering of Mr Barak's support might have accelerated into total meltdown, and the Prime Minister might not have made it on to the aircraft which carried him, battered but still in power, to today's peace summit with the Palestinian leader, Mr Yasser Arafat, in the US.

The tension surrounding yesterday's vote, nevertheless, underlines just how precarious Mr Barak's condition is at present. He enters today's critical Camp David summit a weakened and humiliated leader, without a stable governing coalition and without the firm backing of Israel's parliament.

Yitzhak Levy, the leader of the right-wing National Religious Party, which formalised its departure from the coalition yesterday, in protest against the concessions he fears will be made to the Palestinians at the summit, insists that despite his survival in yesterday's vote, Mr Barak will be negotiating at Camp David without the necessary mandate.

Rabbi Levy is hardly the only critic. Natan Sharansky, leader of the immigrant Yisrael Be-Aliya party which bolted for the opposition benches on Sunday, is accusing Mr Barak of "dividing the nation" and steering the country "in a dangerous direction".

Leaders of the ultra-Orthodox Shas party, who also deserted Mr Barak on Sunday, complain that he has refused to set out any "red lines" for them, limiting the scope of concessions to Mr Arafat. Perhaps the sharpest blow to Mr Barak's credibility, however, has been delivered by his Foreign Minister, David Levy, who, despite professing his continued "partnership with and loyalty to" the Prime Minister, flatly refused to accompany him to the summit.

Levy has intimated that he has lost faith in the Palestinian commitment to peace. Cynics wonder whether this peerless political opportunist has, rather, lost faith in Mr Barak's capacity for remaining in office.

Yet Mr Barak, though potentially poised on the brink of political oblivion, remains unbowed. In repeated addresses these past few days, he has attempted to circumvent his unreliable political peers and appeal directly to the public; insisting that he is seeking peace at their behest; asserting that his 5644 per cent election victory last year over the hardline Benjamin Netanyahu is a more than sufficient mandate for compromise; and promising to bring any deal before them for approval, in either a referendum or new elections.

Amid apocalyptic warnings by Israeli military and intelligence officials that the Palestinians are preparing for a violent confrontation if no dramatic breakthrough is achieved at Camp David, he remains adamant that a treaty with Mr Arafat is possible.

Encouragingly for him, a poll yesterday in the daily Yediot Aharanot showed a majority of Israelis - 52 to 45 per cent - backing him in his journey to Camp David, and 53 to 44 per cent supported his assertion that he does have a mandate to make concessions to the Palestinians.

Still, while Mr Barak may be upbeat about his chances of sealing a deal in the coming days, it is hard to see why. The two sides are far apart on some of the core issues which have so long divided them, especially the future status of Jerusalem and the Palestinian refugee problem.

For a treaty to emerge from Camp David, both sides will be required to make brave, painful compromises of the kind they have hitherto shown precious little inclination to make.

The key factor may turn out to be not Mr Barak's domestic political standing, but Mr Arafat's mindset. Will he be prepared to moderate his positions, in recognition of the fact that Mr Barak may be offering him the best deal he can ever hope to win from an Israeli leader? Or, sen sing Mr Barak's political weakness, will he hold firm to demands for an Israeli pullout from 100 per cent of the occupied territory and other maximalist positions?

Mr Barak is not the only one who will have to sell a deal to his people. Should Mr Arafat moderate his demand, for instance, that East Jerusalem become the capital of a future Palestinian state, his people may well view the deal as an unacceptable capitulation, rather than an honourable compromise, with grave implications for Mr Arafat's continued leadership.

Given the seven years of bickering and delay which have preceded it, the Camp David summit can hardly be expected to yield in a matter of days a full and final deal, in which the two sides settle all the thorny issues and declare an end to the conflict.

The best that can be hoped for, it seems, may be interim progress, with the two sides reaching understandings on some of the cardinal issues, including modalities for a declaration of Palestinian statehood, allocation of water rights, perhaps even the fate of the Jewish settlements, but agreeing to defer other stumbling blocks like Jerusalem and the refugee issue.

The worst-case scenario? Should the summit fail to produce any substantive progress, the two leaders would return to a region likely to deteriorate into another utterly unproductive round of bloody confrontation, more deaths, more lost time and no resolution.

Even in the wake of another such round of violence, after all, the Israeli-Palestinian conflict can only be solved at the negotiating table - and if not by Messrs Barak and Arafat, then eventually by those who will succeed them.