Under the constitution of 1917 as amended, Mexico is a federal republic whose head of state and government is the president, directly elected to a nonrenewable six-year term and assisted by a cabinet. The bicameral National Congress is made up of the Senate, with 128 members serving six-year terms, and the Chamber of Deputies, with 500 members serving three-year terms. Ninety-six of the senators and 300 of the deputies are directly elected, while 32 of the senators and 200 of the deputies are chosen by a system of proportional representation.
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