the twelfth amendment (amendment xii) to the united states constitution was proposed in congress on december 9, 1803. it was ratified by the state legislatures on june 15, 1804. it provided new procedures for electing the president and vice president. before the amendment, each member of the electoral college cast a single vote. the candidate who received the largest number of votes became the president. the candidate receiving the next highest number of votes became the vice president. the twelfth amendment changed the process to the current system whereby one vote is cast for the president and one for the vice president.