Federal Constitution of the United Mexican States (1824)
Of the Duration of the Presidency and Vice Presidency, and the mode of filling Vacancies in each, and of their Oath.
Article 95. The President and Vice President of the Union shall enter on their functions on the 1st of April; and shall vacate their offices, on the same day four years afterwards, by a new and constitutional election.
Article 96. If from any cause whatever, the elections of president and vice president should not be completed and published by the first of April on which the installation is to take place, or the persons elected should not be ready to enter on the office, the functions of the former shall, nevertheless, cease, and the chamber of deputies, voting by states, shall elect a president ad interim.
Article 97. In case the president or vice president be temporarily prevented, what has been prescribed in the preceding article shall take place, and if the impediment were to occur while the congress is not in session, the supreme executive power is confided to the president of the supreme court of justice and two individuals chosen by the absolute plurality of votes of the council of the government. These cannot be members of the general congress, and they ought to possess the qualifications required of the president of the Union.
Article 98. While the elections above spoken of are making, the president of the supreme court of justice discharges the executive power.
Article 99. In the event of perpetual impossibility of the president or vice president, congress, and in their recess the council of government, shall provide for the case according to the 96th and 97th articles, and take steps that the legislatures proceed to elect a president and vice president according to the constitutional forms.
Article 100. The election of president and vice president made by the legislatures, in consequence of the perpetual impossibility of those holding these offices, shall not prevent the ordinary elections which take place the first of September every four years.
Article 101. The president and vice president elected every four years, ought to be on the first of April in the place where the supreme powers of the Union reside, and take an oath before he united chambers to fulfil their duties in the following form: I, -------, appointed president (or vice president) of the United Mexican States, swear before God and his holy evangelists, that I will faithfully discharge the office which the United States have entrusted me with, and that I will observe, and cause to be observed, exactly the constitution and the general laws of the confederation.
Article 102. If neither the president nor the vice president present themselves to take the preceding oath, and the session of congress is open, they shall take such oath before the council of government as soon as each presents himself.
Article 103. If the vice president present himself, and take the oath before the president, he shall be at the head of government until the president has taken the oath of office.
Article 104. The president and vice president, constitutionally appointed according to the 99th article, and the individuals provisionally appointed to exercise the functions of president according to the 96th and 97th articles, shall take the oath mentioned in the 101st article, before the chambers if in session, and if not, before the council of the government.