Hamas and Israel both did not accept Jewish sovereignty in Gaza, and they uprooted the Jews living there. Jewish sovereignty is not recognized on the whole land of Israel: that is why the Arabs control the prayer at the Temple Mount, as I can see it.
I think a good part of this struggle is fear of the wrath of G-d. The last time the Temple was destroyed, it was a serious trama to the entire Jewish people. The Jewish people are hesitant to setup another Temple, to anger G-d, and to get kicked out like the last time, which really has stuck very seriously in the collective conscience of Israel for thousands of years.
But the problem for Olmert right now is that Hamas also does not recognize his sovereignty. Hamas is looking to become the "Taiwan", the small group which controlls ALL of Israeli representation and denies ALL Jewish rights there. But unlike Taiwan, Gaza is not "free", but rather under an religious Oligarchy system.
The secular Jews are hesitant to allow the religious back in power because of fear of the last great Excile, where the religous as well as the secular were removed from Israel. Hamas positions something very similar to the last Excile, in is phraseaology that is very much similar to Iran.
I support National Union simply because they have the eyes to see the situation more clearly than any other politician as far as I can tell. They have not tossed out the "demographic" problem, which really is not a problem at all with only 1.5 million voting Arabs and 5 million voting Jews living in the total militarily controlled Israel. They have predicted the Hamas arrival on the scene. They have an accurate sense of what is occuring, and since they understand the issue, they can deal with it better.
As far as I can tell, the other parties do not understand the problem and are groping in the dark or hiding in the sand. Vote National Union!