The United Mexican States are a federation whose government is representative, democratic and republican based on a presidential system according to the 1917 Constitution. The constitution establishes three levels of government: the federal Union, the state governments and the municipal governments. According to the constitution, all constituent states of the federation must have a republican form of government composed of three branches: the executive, represented by a governor and an appointed cabinet, the legislative branch constituted by a unicameral congress and the judiciary, which will include called state Supreme Court of Justice. They also have their own civil and judicial codes.
The legislature is the bicameral Congress of the Union, composed of the Senate of the Republic and the Chamber of Deputies. The Congress makes federal law, declares war, imposes taxes, approves the national budget and international treaties, and ratifies diplomatic appointments.[94]
The federal Congress, as well as the state legislatures, are elected by a system of parallel voting that includes plurality and proportional representation.[95] The Chamber of Deputies has 500 deputies. Of these, 300 are elected by plurality vote in single-member districts (the federal electoral districts) and 200 are elected by proportional representation with closed party lists[96] for which the country is divided into five electoral constituencies.[97] The Senate is made up of 128 senators. Of these, 64 senators (two for each state and two for the Federal District) are elected by plurality vote in pairs; 32 senators are the first minority or first-runner up (one for each state and one for the Federal District), and 32 are elected by proportional representation from national closed party lists.[96]