Final answer:
The Twelfth Amendment required that the president and vice president be chosen separately through separate elections within the Electoral College.
Step-by-step explanation:
The Twelfth Amendment, ratified in 1804, required that the president and vice president be chosen separately. Before this amendment, the electoral college selected two candidates - one for President and the runner-up for Vice President. The amendment changed the rules so that each candidate would be selected through separate elections within the Electoral College.