The first rule for writing a column is: Don’t make predictions that are any less safe than saying the sun will rise again tomorrow. In fact, better not say that either, since you will look awfully foolish if the sun chooses tomorrow for its first day off.

I should have gone by the rules. Just last week I assured the readers of this newspaper that Ariel Sharon would not leave the Likud and form a new party for the upcoming Israeli elections that will apparently take place in March, since such a step made no political sense. What does the prime minister in his perversity do? Exactly a week later he announces that he is leaving the Likud and forming a new party.

And yet it remains to be seen who has been more foolish: Myself or Mr. Sharon. The latter is engaged in a very big gamble – the biggest he has made since, as a general in the 1973 Yom Kippur war, he crossed the Suez Canal by punching a hole with an armored force between the Second and Third Egyptian Armies. Now he is trying to repeat the maneuver, this time in politics, by exploiting the gap between a Labor Party that has moved to the left, and a Likud that will move to the right, for a new centrist bloc that he hopes will return him to office with greater power than he currently wields.

The mistake I made was more a failure of psychological than of political analysis. Whereas, as I pointed out, Ariel Sharon would have been assured of certain re-election as prime minister had he chosen to run at the head of the Likud, he is now assured of nothing. Campaigning at the head of a hastily cobbled-together party of celebrities that will be, figuratively speaking, all generals and no foot soldiers, he can quite conceivably lose the lead the polls now give him and end up running second to Amir Peretz, the new chairman of the Labor Party, or even – although this is less likely – third, trailing behind the Likud’s candidate, too. (To be elected in a party primary in January, this will most probably be Benjamin Netanyahu.)

And yet as I also pointed out last week, a victory at the head of the Likud, while certain, would have left the prime minister with relatively little freedom of action, especially in terms of Israel’s conflict with the Palestinians. Prevented from renewing his present coalition with Labor by the rightward-pulling forces in the Likud that rebelled against the Gaza disengagement, on the one hand, and on the other hand, by a Labor leader who is the most leftward-leaning that party has had for decades, he would have had to govern by a coalition of the Right that would have tied his hands and kept him from implementing the future disengagements in the West Bank that he believes are in Israel’s best interest.

What I misjudged was Ariel Sharon’s response to this dilemma. I should have realized that the man who, in 1973, chose the risky offensive tactic of crossing to the Egyptian side of the Canal over remaining in safe defensive positions on the Israeli side, would prefer in 2005, to go for broke again. At the age of 77, Mr. Sharon, it now is clear, does not want to serve out one last term as a prime minister who cannot accomplish bold things. He wants a party of his own that will do what he tells it to – and which, if he wins, will agree to forge a coalition with Labor and press ahead with his disengagement strategy.

Yet there are some serious “ifs” in this scenario quite apart from the question of whether Mr. Sharon can win the elections. Even if he can, it’s not clear that he and Amir Peretz can find enough common ground for a coalition. And even if they do, and Mr. Peretz abandons his belief in a negotiated settlement with the Palestinians (which Mr. Sharon puts no credence in) and climbs on the unilateral disengagement wagon in return for being handed the steering wheel of the government’s economic policies, it’s not clear that Mr. Sharon will be able to hold his new party together. The prime minister who could not impose his will on the Likud, in which he was a dominant figure since being instrumental in founding it in 1974, will not necessarily be able to impose it on the Knesset members of his new party, many of them high public figures more used to giving than taking orders and not easily shackled by parliamentary discipline.

Indeed, one cannot help wondering whether, had Mr. Sharon invested just a part of the energy that he will have to put into his new party in strengthening his ties within the Likud, he couldn’t have continued to accomplish his ambitions at the head of it. And by the same token, one has to ask whether the high-handedness with which he ran the Likud, and which led to an insurrection against him, will not once again get him into trouble with his new party. Second marriages only work out well when one has learned from the mistakes of the first.

Ariel Sharon has a vision and wants to implement it. In this sense, his many critics on both the Left and the Right who accused him of carrying out disengagement as a mere ploy for remaining in power while under investigation on corruption charges owe him an apology. At this point in his life, he clearly cares about disengagement more than about power. But he will need power to continue disengaging, and he may have chosen the wrong way of getting it. This time I’ll make no predictions. Time will tell.

Mr. Halkin is a contributing editor of The New York Sun.