Passed by Congress: 9 December 1803
Ratified: 15 June 1804
The Electors shall meet in their respective states and vote by ballot for President and Vice-President, one of whom, at least, shall not be an inhabitant of the same state with themselves; they shall name in their ballots the person voted for as President, and in distinct ballots the person voted for as Vice-President, and they shall make distinct lists of all persons voted for as President, and of all persons voted for as Vice-President, and of the number of votes for each, which lists they shall sign and certify, and transmit sealed to the seat of the government of the United States, directed to the President of the Senate; -- the President of the Senate shall, in the presence of the Senate and House of Representatives, open all the certificates and the votes shall then be counted; -- The person having the greatest number of votes for President, shall be the President, if such number be a majority of the whole number of Electors appointed; and if no person have such majority, then from the persons having the highest numbers not exceeding three on the list of those voted for as President, the House of Representatives shall choose immediately, by ballot, the President. But in choosing the President, the votes shall be taken by states, the representation from each state having one vote; a quorum for this purpose shall consist of a member or members from two-thirds of the states, and a majority of all the states shall be necessary to a choice. And if the House of Representatives shall not choose a President whenever the right of choice shall devolve upon them, before the fourth day of March next following, then the Vice-President shall act as President, as in case of the death or other constitutional disability of the President. The person having the greatest number of votes as Vice-President, shall be the Vice-President, if such number be a majority of the whole number of Electors appointed, and if no person have a majority, then from the two highest numbers on the list, the Senate shall choose the Vice-President; a quorum for the purpose shall consist of two-thirds of the whole number of Senators, and a majority of the whole number shall be necessary to a choice. But no person constitutionally ineligible to the office of President shall be eligible to that of Vice-President of the United States.
The presidential election of 1800 turned into a complete mess in the Electoral College, demonstrating serious weaknesses in the Constitution's original design of presidential elections. In 1800—one of the most important elections in American history—Thomas Jefferson defeated the incumbent president, John Adams. However, Jefferson managed to finish in an exact Electoral College tie with Aaron Burr, who was supposed to be his own vice-presidential running mate. The problem was that the Constitution's original design for presidential elections called for each member of the Electoral College to cast two votes, for his top two candidates for the presidency. When all the ballots were tallied, whoever finished first would become president, and whoever finished second would become vice president. But this system didn't account for the development of political parties and partisan presidential/vice-presidential tickets. In 1800, Jefferson's supporters in the Electoral College each voted for Jefferson and Burr; when the two men finished in a tie, it meant that the entire election was thrown into the House of Representatives, which could have voted for anyone. In the end, Jefferson's great political rival Alexander Hamilton convinced members of his own party to defer to the will of the people and allow Jefferson to become president, but any manner of mischief could have occurred. (Burr was rumored to be working to steal the presidency out from under Jefferson's nose.) In order to prevent such a debacle from happening again, the Twelfth Amendment split the balloting for the presidency from that for the vice-presidency; under the Twelfth Amendment, Electors now cast separate ballots for president and vice president.