why was the twelfth amendment added to the constitution?
It was added so that the president and Vice President would be from the same political party.
The 12th Amendment provides the procedure for electing the President and Vice-President and was added to the U.S. Constitution, replacing Article II, Section 1, Clause 3 on June 15, 1804. It replaced the original procedure because the original was causing problems with elections in 1796 and 1800.