I think there’s a big point being overlooked here. Two right-wing parties, Eli Yishai’s Yachad and Avigdor Lieberman’s Yisrael Beitenu are both on the borderline of being polled just over the make it or break it line of getting into the Knesset with four or five seats. The polls can be off by a few seats. If either or especially both these parties miss the cutoff and just miss getting into the Kenesset, then the right-wing is literally blowing anywhere between 3 and 7 seats. That changes the entire paradigm and mathematics. One or both of them failing to get in, thus wasting all those right-wing votes, can literally hand over the majority to Herzog. And I don’t think this scenario is very far fetched at all.
(And the left-wing is at much less risk of a similar scenario as they have only one small party on the borderline, Meretz, and it is polling better than both Lieberman and Yishai.)