A constitution is an agreement on the rules of the relationship between the government and the people. It makes clear rules about which institutions have the power to make which decisions. This is very important in a democracy because different parts of government need to be free from the power of other parts.

By separating powers and responsibilities amongst the various institutions of government, constitutions act as an organizational chart for the government.

The parts of a constitution that outline the institutions and offices of government establish issues such as:

• The system of government (i.e. parliamentary, presidential or semi presidential)

• The form of the state (unitary or federal)

• The extent to which government power is decentralized

• Power-sharing arrangements

The political systems established by a constitution have an important impact on political parties. The political system they establish affects the position, role and organizational structures of political parties. For example, the choice between a presidential, parliamentary or semi-presidential system greatly influences a party’s ability to gain and use power.

In other cases, if the constitution establishes a more decentralized governance system, this might require parties to focus more on regional branches. Alternatively, constitutional requirements for women’s or minority quotas may require parties to change their participation and internal selection policies. Because these various structures have a significant impact on political parties, parties often play an important role in drafting or reforming constitutions.