Eli Yishai - Yachad dropping out of the race and throwing his support to UTJ can be massive.

UTJ was already pushing the seventh mandate. It was almost definite they would achieve it, possibly dependent on final turnout numbers. Now with Yachad and [many of] their supporters voting UTJ, they will definitely get the 7, and almost definitely even the 8th. Nobody really knows how much support Yachad and Eli Yishai actually have, and the numbers form last time are definitely not accurate for this election, as many of his supporters from back then will have moved on to other parties by now, but surely he has a nice amount. The question is basically if this will get them 8 or 9 mandates.

That is massive for UTJ.

And it is a big hit for Shas. Many past Shas voters have already been planning to vote UTJ anyway. Many past Shas voters are searching for other parties, such as Zehut, Otzma Yehudit, Likud, and probably others as well. That's why Shas is hovering around 4 mandates in all the polls. If this move by Yachad towards UTJ pulls another several thousand voters away from Shas and to UTJ, that could be a big hit to Shas and might push them under the threshold for good.

Of course the polls always get Shas wrong anyway, even more than they get the rest of the parties wrong. So the polls saying Shas get 4 might actually be 6 or 7 and then Yachad brings them down to 4 or 5. We cant really know, but it is definitely a big hit to Shas.

This might save thousands of votes that would have been lost by Yachad not passing the threshold, but it might cause a hundred thousand or so votes for Shas to be thrown out if Shas doesnt get through because of this.