The departure of Ariel Sharon from the Middle East political landscape casts a new question mark over the Israeli-Palestinian peace process, at the very time when a combination of Mr. Sharon's own ambitions and renewed US interest in tackling the conflict had lifted hope for progress.
Indeed, his hospitalization has stalled momentum among Israeli moderates - the one group that, under Sharon's leadership, might have provided significant advances toward a final settlement, analysts say.
"If they manage to show cohesion, maybe these centrist forces do actually push things ahead, but that's the only variable out there," says Robert Satloff, executive director of the Washington Institute for Near East Policy. "It's not the Palestinians, and it's not the US."
In its five years, the Bush administration has been reluctant to press for bold steps from the parties, and it's unlikely to alter that pattern now, many experts say. Officially, neither the White House nor the State Department is offering much diplomatic direction for the post-Sharon era, suggesting that doing so would be distasteful as the prime minister fights for his life. Secretary of State Condoleezza Rice postponed a trip to Australia in order to be in Washington at a crucial juncture in Middle East affairs, while diplomatic sources said the White House was quietly making contingency plans in the event of Sharon's passing.
But even as Secretary Rice expressed faith last week in the Israeli people's continuing desire for peace and the Palestinian people's determination to build a democracy, the trip of two US diplomats to the region to keep foundering Palestinian elections on track was postponed. Those elections are scheduled for the end of this month, but the heightened popularity of the radical group Hamas has led to speculation that Palestinian President Mahmoud Abbas might use some pretext, including Israel's political uncertainty, to push back the date.
Still, some observers do see potential for US leadership - if the United States so chooses - after the departure of such a dominant and unilateralist leader as Sharon. A controversial military and political leader for decades, Sharon responded skillfully to the 9/11 terrorist attacks by emphasizing the commonality of the threat the US and Israel face. In so doing, he removed virtually all daylight from between the two countries - an accomplishment that buoyed Israel's supporters in the US, but which some critics say damaged the US role as an "honest broker" in the conflict.
President Bush was not personally close to Sharon the way he has been with Britain's Tony Blair. But at the same time, Mr. Bush seemed to identify with Sharon's "peace through strength" approach and a resort to unilateral action, even when it ran counter to US policy.
Nothing groundbreaking is likely to happen in the short weeks before Israeli elections are held March 28 - weeks that will be under the stewardship of Acting Prime Minister Ehud Olmert.
Israeli voters, who appeared poised to follow Sharon's vision for effectively setting the borders for both Israeli and Palestinian states, will now be sizing up potential bearers of his mantle. "I would say Ehud Olmert has an audition with the Israeli public that is significant," says Jennifer Laszlo Mizrahi, founder of the Israel Project in Washington.
Yet Mr. Olmert would be a less imposing figure than Sharon (even though he is the source and chief supporter of many of Sharon's ideas, such as disengagement from Gaza). Thus an Israeli government under someone like Olmert might open the door wider to American diplomatic action, some experts believe.
"Under Sharon, he was the architect, and the US was basically following," says Stephen Cohen, national scholar at the Israel Policy Forum in New York. "But with somebody like Olmert, there is more of a chance of the US being more of an architect."
But taking a leadership role in the process would be a departure for the Bush administration. It has primarily taken a "wait and see" approach to the conflict since it decided early on that it could not work with Palestinian leader Yasser Arafat.
Mr. Arafat's death in November 2004 prompted the administration to speak of new opportunities for peace. More recently, Rice's personal involvement in the brokering of an agreement on border crossings from Gaza raised hopes in some circles of a more robust US engagement.
But others caution that such hopes may have been wishful thinking. "I don't know of anyone in the high levels of this administration who saw [Rice's role in the Rafah crossing agreement] as a precursor of diplomatic engagement," says Mr. Satloff of the Washington Institute. In the same way, he adds, expecting a new US direction as a result of Sharon's departure from the scene may be going too far.
Still, the potential combination of new, peace-seeking Israeli leadership and solidified Palestinian leadership might open the diplomatic door.
"I don't think we've seen [a desire to play the role of architect] yet in this administration, and it's still difficult to say if it will emerge as a result of this change [of Israeli leadership]," Mr. Cohen says. "A lot will depend for the US on the Palestinian elections and whether a leadership emerges that the US can work with."
Even that, of course, could turn out to be too bright a forecast. Some analysts predict Sharon's dream of forging a grand coalition of the Israeli center will now fail, leaving the country mired in a left-right split. And with Hamas gaining support among Palestinian voters, the potential remains for turmoil that would stop any peace moves cold.
Add to this the complicating factor of "changing self-perceptions" for both sides of the conflict, as Cohen calls the deep changes now shaking Israeli and Palestinian societies. "For Israelis, it's a receding of the belief that they are organized around maintenance of the territories," he says. "And for the Palestinians, are they in a position to say that pursuit of peace and a Palestinian state will be able to replace that part of their identity linked to the rejection of Zionism?"
Such complexities help explain why Bush, hosting Mr. Abbas at the White House in October, said he didn't know if there would be a Palestinian state by the time he left office.
"It's not the moment for diplomacy when 40 percent of the Palestinian legislature could be represented by Hamas," says Satloff. As for Cohen, he sees another motivation for Bush's public nonchalance about the timetable for a Palestinian state: "He wants to keep open what constitutes success in his Middle East policy."