I'd go further than that. The purpose of Operation Cast Lead was to improve Livni and Barak's standing in the polls in the forthcoming Israeli national elections. Which is why Operation Cast Lead duration was lengthemed and which is why the IDF resorted to destroying civilian infrastructure, because the alternative was entering Gaza City taking casualties and thus impacting on Livni's and barak's polling figures.
Court rejects plea bargain from former PM Olmert, adding one month to jail sentence (Haaretz)
from the article: What led to IDF bombing house full of civilians during Gaza war?