If there is any politician in Israel who must be eating his own heart out now, it is Benjamin Netanyahu.

Imagine the following:

Suppose that, two years ago, when Ariel Sharon first sought to set his unilateral Gaza disengagement plan in motion by bringing it to a Likud referendum that he lost, Mr. Netanyahu had supported him wholeheartedly. Suppose that, instead of avoiding backing the plan publicly while criticizing it privately, Mr. Netanyahu had gone out and campaigned for it vigorously. Suppose that, as a result, Mr. Sharon had won the referendum as he had thought he would. Mr. Netanyahu, who had been vying since the mid-1990s for the party’s leadership with Mr. Sharon, could certainly have changed the minds of that ten percent of the referendum’s voters that was needed to reverse the outcome.

Suppose, too, that with the anti-disengagement forces within Likud squelched, and Ariel Sharon grateful for Mr. Netanyahu’s support, the latter had continued to function as the excellent finance minister that he was while remaining loyal to his prime minister. Suppose that, when the withdrawal from Gaza took place last summer, Mr. Netanyahu had once again backed it firmly rather than hem, haw, and resign from the government in protest at the last moment.

And suppose that Ariel Sharon, still securely at the head of the Likud, in large measure thanks to Benjamin Netanyahu, had never bolted it to found his new Kadima Party. Suppose, therefore, that the elections originally scheduled for November 2006 had not been advanced to March. And suppose that Ariel Sharon had then had the massive stroke that he had last week. What, politically, would have happened?

The answer is obvious. As a former prime minister, a highly successful finance minister who had turned a sluggish economy around by courageously implementing a series of badly needed reforms, and a highly popular Likud figure for whom Mr. Sharon’s associates would have felt only appreciation, Benjamin Netanyahu would have inherited the party’s leadership. Even if Likud cabinet minister Ehud Olmert, the acting prime minister, had sought to contest the position, Mr. Netanyahu would have beaten him hands-down, in plenty of time to gain the party’s nomination for the November elections and to win them by a large margin.

Whereas now…. well, now Benjamin Netanyahu is the leader of a drastically shrunken Likud and Ehud Olmert, who took over the finance ministry when Mr. Netanyahu left it, is at the head of Kadima. If the new party continues to hold together as surprisingly well as it has in the days since Ariel Sharon’s incapacitation, and to show as much strength at the polls, Mr. Olmert will be elected prime minister in March. One can imagine what Mr. Netanyahu must have been thinking this week as Mr. Olmert announced that he would carry on when elected with “his” and Ariel Sharon’s economic policies, without so much as mentioning the man who was most responsible for them.

Mr. Netanyahu must be particularly kicking himself because, despite his assertions to the contrary, it is hard to believe that his objections to the withdrawal from Gaza were every really very principled. He has always touted himself as a hawkish pragmatist rather than as an ideologically rigid “undivided land of Israel” supporter, and the Gaza disengagement and hawkish pragmatism were perfectly consistent. His decision not to back disengagement was far more a question of political tactics and political opportunism; by doing so, he thought, he could outflank Ariel Sharon on the right and take back from him the same Likud of which he had lost control in 1999.

To be sure, if Kadima weakens seriously in the weeks and months ahead, Mr. Netanyahu still has an outside chance of winning the March 28 elections, in whose race the polls now show him running third, behind Mr. Olmert and Labor candidate Amir Peretz. Much depends on the quality of leadership Mr. Olmert demonstrates between now and then, as well as on the security situation.

Although Mr. Olmert will do everything to appear to be the executor of Ariel Sharon’s legacy, one might remember that Shimon Peres was in a similar situation after the assassination of Yitzhak Rabin in November 1995. Mr. Peres began his campaign against Benjamin Netanyahu in the 1996 elections with a huge lead, much of it due to the public’s perception that he was wearing Mr. Rabin’s mantle, only to see it dissipate due to a rash of Palestinian terror attacks.

But there is a major difference between those elections and this year’s, too. In 1995-1996, even before the last-minute upsurge in terror, the Israeli public was in a state of disillusion with the Oslo Agreement that ultimately prevailed over its shock at Rabin’s assassination and its desire to honor his memory. In 2005, in the months preceding Ariel Sharon’s strokes, it was in an increasingly hopeful mood. Indeed, for the first time since the assassination Israelis were beginning to feel that there was, in Mr. Sharon’s unilateralism, a way out of the dead-end into which Oslo had plunged them.

Ehud Olmert’s task in the coming campaign is to convince Israelis that he can carry out elsewhere what Ariel Sharon started to do in Gaza. The question is not whether he would like to try; on the contrary, he was publicly arguing for unilateral withdrawals far in advance of Mr. Sharon, whose “point man” he was perhaps acting as. The question is whether he can pull the country along behind him. “He doesn’t have much charisma,” I said the other day to a friend. “Neither did Harry Truman when Roosevelt died,” was the answer. It’s an interesting comparison.

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