Ian MacKinnon, Jerusalem Correspondent of The Times, analyses Ariel Sharon's decision to leave Likud and fight a snap election as leader of a new centrist force - a decision that transforms the landscape of Israeli politics

"It's already been compared to the eruption of a volcano and that's a fair enough description. It's the tectonic plates of Israeli politics shifting, an earthquake - it's huge. This will reshape Israeli politics in a way that's not been seen for decades, with big implications for the peace process and for the direction of any peace process.

"Essentially, this is being widely perceived, unanimously perceived, by commentators here as Mr Sharon's bid for his place in history. He felt that he had reached the end of the road with Likud, which was frustrating him at every turn over the planned pullout from Gaza. With the arrival of the new Labour leader, Amir Peretz, last week, and his decision to pull Labour out of the Government, Mr Sharon could not continue any longer.

"It's also being widely perceived as a move to set the borders, Israel's final borders, which will mean withdrawing from some of the more remote settlements in the West Bank and consolidating the state of Israel's hold on Jerusalem and large settlements around the city. By doing that they can get close to some kind of final peace settlement in the four-year term of the next parliament.

"It's interesting, because Amir Peretz said last week that he was going to focus on social issues, because under Likud a lot of the poorer Jews in development towns have been made considerably worse off. Those are Mr Peretz's constituents. He wanted to move away from the perennial issue of Israeli politics, security, security, security with everything else taking a back seat. It now remains to be seen whether the focus really will be on that now, because Ariel Sharon's move has shifted the focus back towards peace with the Palestinians.

"Mr Peretz has said that he wouldn't work with Likud, and he's withdrawn from the Government as he stands. But Labour joined the coalition originally to help get disengagement through, so if Sharon's policies are for more disengagement, or withdrawal, then perhaps Peretz can work with him on that.

"Binyamin Netanyahu is the favourite to assume the leadership of Likud, but that's not necessarily certain. There are six others who have shown an interest, including a couple who have already thrown their hats into the ring.

"As for Shimon Peres, the ousted Labour leader, he spoke to Mr Sharon yesterday and people are saying that he has been invited to join the new party, but he's been Labour all his life and that would be seen as a betrayal. So maybe he would have some kind of senior statesman role in a future coalition.

"Overall, this is a massive gamble by Mr Sharon, a gamble for his place in history. He could not grab that place with Likud sitting on his back, so he's cast them off, even though he founded the party."

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