The 12th Amendment provided for separate Electoral College votes for President and Vice President, correcting weaknesses in the earlier electoral system which were responsible for the controversial Presidential Election of 1800.
Or you could say
The Twelfth Amendment stipulates that each elector must cast distinct votes for president and vice president, instead of two votes for president. ... The Twelfth Amendment requires a person to receive a majority of the electoral votes for vice president for that person to be elected vice president by the Electoral College.