The Twelfth Amendment, ratified in 1804, requires presidential electors to cast separate ballots for president and vice president instead of voting for two candidates on a single ballot. Before this change, the candidate with the most electoral votes became president while the runner-up became vice president, creating awkward pairings like political rivals John Adams and Thomas Jefferson in 1796. The 1800 election between Jefferson and Aaron Burr ended in a tie because electors couldn''t distinguish their presidential choice from their vice presidential choice, forcing a contentious House vote that took 36 ballots. The amendment solved this by mandating distinct ballots and changing contingent election procedures: if no presidential candidate wins a majority, the House selects from the top three vote-getters; if no vice presidential candidate wins, the Senate chooses between the top two. Electors meet in each state on the first Monday after the second Wednesday in December to cast their separate votes.