Sharon is a member of the Likud party, and is answerable to it. That is a main part of our parliamentary system, a system to which we returned after a brief debut into the direct-election system.

Another way of looking at it: working against the express policy of their own party is what got Netanyahu and Barak into elections so soon. I would expect for Sharon to learn from other people's mistakes.

Of course, in this case, it won't matter, since it's not likely that Labour can stay in this government very long without losing what little credibility they had, and others are likely to follow.