At the heart of Prime Minister Sharon’s “Disengagement Plan” lies the observation that in the short run a formal peace with the Palestinians will elude Israel. This owes to the chronic weakness of Palestinian moderates — an evaluation underscored in a recent CIA report that predicted there would be no Israel-Palestinian peace agreement before 2020. It is exacerbated by international pressure, including from the Bush administration. Combined with Palestinian terrorism, it’s hard to see the logic of holding out hope for a deal with the Palestinian Authority, with or without Yasser Arafat.

As for who should make the judgment call, Israeli voters have twice chosen Mr. Sharon after hearing him say he would work to end terrorism and work toward a political solution. As premier, he bucked majorities in his own party to advocate a Palestinian state. He led a reluctant and divided Cabinet in accepting the Road Map based on the principles enunciated on June 24 of last year by President Bush. The most important statement by Mr. Sharon at Herzlyia last week was his reminder that “for peace, as well as for war, we must have broad consensus.”

This was more than a plea for the opposition Labor Party to join his government, as insurance against the possibility of a decision by the rightist parties to quit. The premier has displayed nothing if not a keen appreciation of public opinion, which favors above all a separation from the Palestinians. If such a separation cannot be achieved through negotiations, what is the logic against a unilateral redeployment behind the security fence? Certainly it will be hard to second-guess him from the left. For he has, with some modification, adopted the very platform of the man against whom he ran in the last election.

The difference between the Sharon plan and that of Amram Mitzna is that the Labor candidate would have drawn a line of separation closer to the 1967 de facto border. Otherwise, the two plans are remarkable for their similarity. Mr. Sharon’s plan has roots on both sides of Israel’s divided political aisle. To the right, he is saying that his plan is the only alternative to a process in which Israel will be pushed back to the 1967 lines, through the hoax of a “peace process” with the Palestinians. On the left, Mr. Sharon’s vision shares the assumptions of the plan formulated by the late Yigal Allon, which served as Labor Party policy before Oslo.

According to both plans, Israel would maintain a sizable Jewish demographic majority while keeping those parts of the territories seized in the 1967 war necessary for its defense. This was called “territorial compromise,” because it insisted there would have to be a compromise over the disputed territory. It took center stage for a decade, against both the more dovish formula, “territories for peace,” and the less forthcoming “functional compromise” formula, which did not foresee substantial territorial concessions. Mr. Sharon’s plan is also an attempt to seize center stage from the “Let’s make a deal” left and the “Not an inch” right.

However, there are significant dangers associated with such a course, chief among them the probability that once Israel withdraws to its new deployment, the Palestinians and their backers will insist on reopening negotiations. The key to the Disengagement Plan lies in Israel’s abili ty to withstand pressures to continue to yield concessions, at least until such time as the Palestinians end terrorist activity.

There is another danger. Proposing, as Mr. Sharon’s Cabinet ally Ehud Olmert does, that “tens of thousands” of settlers will be involved in the redeployment, will undoubtedly provoke a reaction from the pro-settler right. Israelis will be fighting among themselves for a dubious prize — separation, not peace and normalization.

However, on a net basis, our guess is that Israel’s polity will reckon the benefits of Mr. Sharon’s plan outweigh its costs. And it would be folly for the Bush administration, which has set the diplomatic clock ticking toward a Palestinian state, to oppose Israel’s imposition of a six-month timeline to test Palestinian intentions. Mr. Sharon’s plan may rescue the Road Map by forcing the Palestinians to prove their readiness to make peace or risk an Israeli redeployment that will leave them with less of the territories than they likely would achieve through an honest negotiating process. Meanwhile, America’s work can focus on the building of a democratic Arab example in Iraq.