What event helped lead to a change in the way the electoral college chose the preisdent and vice president?

Answer 1

The emergence of political parties and nationally coordinated election campaigns soon complicated matters in the elections of 1796 and 1800. According to the prevailing rules of electoral college voting at that time, electors cast votes for two persons. Electors could not distinguish between their presidential and vice-presidential choices until the passage of the Twelfth Amendment to the United States Constitution in 1804. In 1796, the recipient of the most electoral votes would become president and the runner-up vice-president. The United States presidential election of 1796 was the first contested American presidential election and the only one to elect a President and Vice President from opposing tickets. Although John Adams won, Thomas Jefferson received more electoral votes than John Adams' vice-presidential running mate Thomas Pinckney and Jefferson was elected Vice-President. Responding to the problems from those elections, the Congress proposed the Twelfth Amendment in 1803 - prescribing electors cast separate ballots for president and vice president - to replace the system outlined in Article II, Section 1, Clause 3. By June 1804, the states had ratified the amendment in time for the 1804 election.