It is likely that those Netanyahu supporters who despise Lieberman, or those Lieberman supporters who look down on Netanyahu, will have a very hard time voting for a joint ticket.
Question: Suppose that the Likud and Hadash parties decide to run on a joint ticket in the upcoming elections. How many votes would they get? The answer: Most likely zero. Why? Because there is not even a single person who simultaneously supports both Likud and Hadash.
The sure votes that go to a merger between two parties are cast by people who support them both. Now let us suppose that Likud and Yisrael Beiteinu run on a joint ticket (this has already happened, but it still seems like a nightmare). In mathematical terms, the joint ticket's pool of sure votes is the intersection of the group made up of Likud supporters and that made up of Yisrael Beiteinu supporters. Its size does not exceed the size of each party on its own.
Obviously, there are those who support Likud but not Yisrael Beiteinu, or vice versa, and who will also vote for a joint ticket. But it is likely that those Netanyahu supporters who despise Lieberman (and there are such people in the government), or those Lieberman supporters who look down on Netanyahu (there are more than a few of those too ) will have a very hard time voting for such a joint ticket. And a person who is neither a Likud nor a Yisrael Beiteinu supporter has no reason to vote for Likud-Beiteinu. The upshot is that the number of seats that Likud-Beiteinu can expect is most likely smaller than the combined sum of seats each party would get on its own.
The history of similar attempts by Israeli political parties suggests the same conclusion: The number of seats won by joint-tickets is smaller than the sum of their parts. Why then did Netanyahu decide to drop this bomb, to carry out this political nuclear fusion? The answer, ostensibly, is his survival instinct. Presumably Netanyahu, who is experienced in the art of ruling through well-organized fear mongering - fear of Iran, of the Arab Spring, of foreigners, of an economic meltdown a la Greece - has succumbed to his own fears and initiated a process that would guarantee his place at the head of the largest party in the Knesset. Such an outcome would seemingly also promise better "governance" - a chilling concept when Netanyahu and Lieberman are those at the helm. Perhaps he was also motivated by the hope that the criticism directed at him - that he talks much but does little, that he essentially avoids governing (he would have us believe that this is because of the "system" or the constraints of the coalition, but it is really because of his character ) - would abate in his third term in office, a period which will supposedly be so abundant in action and governance that it will make us miss his hollow words.
In fact, what motivated Netanyahu was not a survival instinct, but a death wish. Had he announced back in May that Israel will go to elections in September, instead of zigzagging into the short-lived union with Kadima, he would have now already been victorious. But, just as he single-handedly undermined his own popularity in the beginning of May, and then again in July (with the dismantling of the Plesner Committee and the divorce from Kadima ), so did he sabotage his interest again now, at the end of October.
The far-right monster does not only terrify leftists and centrists; it also frightens many on the right and in the Likud itself. Many voters are now expected to leave the party for Yair Lapid's Yesh Atid, for the Labor Party and for Shas. If Netanyahu was worried that an Aryeh Deri-led Shas party would cease to support him, this scenario has only become more realistic after the creation of Likud-Beiteinu. This party would probably be the largest in the Knesset, but, as in the case of Kadima in the previous elections, it is doubtful that it will be charged with forming the government.
Unlike other commentators, I see no need for the center-left block to merge and run on a single ticket. Such a move will only weaken it. It should sit back and let Netanyahu destroy himself. This way, at least, he won't destroy us.