Ariel Sharon's massive stroke and slim chance of a full recovery has thrown both Israeli politics and the Middle East peacemaking process into turmoil.

Even if he does survive the stroke that felled him on January 4, Sharon's chances of remaining prime minister and delivering the huge victory his newly-formed Kadima party was expecting in Israel's general election in March look remote.

Many fear Sharon's absence will leave a political vacuum that will be difficult, if not impossible to fill and make the path to peace with the Palestinians still harder.

"He formed the Kadima, people had a tremendous amount of confidence in it" Aurel Braun, professor of international relations at the University of Toronto told CTV's Canada AM.

"He was someone who wanted peace and would make major concessions for peace. But at the same time he was willing to protect the population. This is why the party was so popular."

As with the assassination of former prime minister Yitzhak Rabin in 1995, Sharon's deteriorating health marks the second time in modern Israeli history that a leader who had come to see the need for compromise with the Palestinians appears to have been cut down in mid-stride.

Sharon made history with his controversial withdrawal of Israeli settlements in the Gaza Strip in August 2005, and most recently by stepping down from the ruling Likud party he helped create to form the new, centrist Kadima party.

Opinion polls suggest that with Sharon at its helm, Kadima would have defeated Likud at the March elections.

However without his leadership, those who followed Sharon from both the left and right to form the new party may disband and return to their old Labour and Likud Party loyalties, Braun told CTV News.

"Without Ariel Sharon, without this figure who had been so large in Israeli politics for so long ... the party's not likely to hold together," Braun added.

Currently, Sharon's deputy Ehud Olmert has stepped in as prime minister. Under Israel's constitution, the deputy leader takes over if the PM becomes incapacitated.

After 100 days, the country's president begins the process of forming a new governing coalition. If the prime minister dies, cabinet chooses a replacement for him.

Although no natural successor stands out, there are several candidates in the running to replace Sharon in the event of either his death or the possibility that he will be unable to return to his post.

The likely candidates include his deputy Olmert, who is a capable politician but lacks a national following.

Shimon Peres, the former Labour leader who defected to Kadima, is another possibility. However he is widely distrusted and his age, 82, may also be a strike against him.

Other possibilities include Justice Minister Tzipi Livni, and Defence Minister Shaul Mofaz.

None, however, possess the political clout Sharon holds and none emerge as a clear choice.

"I think nobody is going to really fill his shoes so to speak, and the situation is really putting Israel not in a state of turmoil, but it's going to join the rest of the Middle East countries in a state of uncertainty," Atif Kubursi, United Nations development officer for the Middle East, told Canada AM.

"The delays that this will really bring and the difficulties, the complications it's likely to bring forward too. It's going to complicate the peace process ... but certainly the Palestinians feel today, ironically, that a dead Sharon is far worse than a living Sharon," Kubursi said.

Without Sharon in power, the state's future could change drastically. Israel's parliamentary elections are still scheduled for March 28, and if Sharon's Kadima party does not mount a challenge without his leadership, it's very likely that the Likud party will win the election.

Likud is led by Binyamin Netanyahu, who would most likely halt the disengagement plan immediately.

Up to now, the Gaza disengagement has been carried almost entirely by the momentum of Sharon's vision and personality.

While some Palestinians have reacted by celebrating Sharon's deteriorating health, others are apprehensive about the future of the region. Among Palestinians the controversial leader is alternately considered a friend and formidable enemy.

Palestinian Prime Minister Ahmed Qurei said his people would pray for Sharon's speedy recovery. His illness has massive implications for Israel and the entire region, he said.

"We are looking all the time for a leader in Israel to be in favour of peace and ready to sit with Palestinians to start very serious and credible negotiations," he told the BBC.

The Palestinian labour minister Ghassan Khatib said Sharon's illness was significant for the region, but he fell short of praising him.

Khatib described Sharon as one of the most important political personalities in the Middle East, and that his absence would have a sharp effect on politics.

However, Khatib said Sharon had not improved peace or security in the region, so his absence wouldn't harm peace prospects.

Meanwhile, Palestinian politics is in turmoil. Mahmood Abbas, the man the Palestinians elected president after the death of Yasser Arafat in 2004, has proved incapable of administering either the West Bank or the Gaza strip.

And in the Palestinian parliamentary elections in January, the violent Islamic extremists Hamas are expected to do well against Abbas's ruling Fatah party.

Israel is calling for Hamas to be disqualified from the elections.