Who really rules Israel?

In light of the battle between Olmert, Netanyahu and Barak for the next premiership, the public debate focuses on the question on who of these three politicians is the "strong leader" many Israelis yearn for. At the same time, the failures of all Israeli leaders throughout history and their inability to implement their policies are attributed to a series of elements, including political instability, the plethora of parties, and the low popularity of all government institutions.