Trias

The favorite government structure nowadays is often called the Trias Politica (三權分立), with independent executive, a legislature, and a judiciary powers.

I shall not soil my hands and join the discussion of an independent judiciary. There are, however, a fourth domain for running a government that may skip your eyes.

Take aside judiciary, they are:

• proposal of a policy
• decision on a policy (i.e. legislature)
  
• execution of a policy (i.e. executive power)

The last of which is usually straightforward and almost always relies on civil servants. It is the first two that often cause the problem. Take Britain as an example, policies are mostly proposed by the cabinet or the dominant party, and endorsed by the parliament - in which you could hear the voice from the opposition, but is essentially controlled by the same group of people from the dominant, so much so that policies could move forward.

PS. For those who have a grip on British politics, or did read the masterpiece of Jonathan Lynn and Antony Jay, you may know the civil servants (i.e. the executive power) have much indirect influence on the proposal and decision of policies. That's another story.