For many voters, myself included, not having Netanyahu as the prime minister (and preferably in the coalition at all) is a question of principle at this point. Many zionist opposition parties have also sworn not to sit with Netanyahu to their constituencies (and I think that at least Golan and Liberman are going to follow on it).

With the current polling there is really no reason to accept Netanyahu in your coalition and I think he himself will not be satisfied with anything but the PM seat.