The planning started in late summer or early fall. It was well underway during the period where the cease fire was working. The opening date of Cast Lead was decided at that time. The Olmert government had decided almost three months before to start Cast Lead on 27 December, 2008 and Israel unilaterally declared a cease-fire with all troops withdrawn by 21 December less than three weeks before the elections. The dates when Cast Lead was planned and approved, the timing and of it's initiation, and the timing of it's ending certainly seem to indicate that it was a war fought to benefit Kadima and Labor in the elections.
Mexico sentences five men to 697 years for killings of 11 women (AP)
from the article: What led to IDF bombing house full of civilians during Gaza war?