Twelfth Amendment to the United States Constitution

The Twelfth Amendment (Amendment XII) to the United States Constitution provides the procedure for electing the president and vice president. It replaced the procedure in Article II, Section 1, Clause 3, under which the Electoral College originally functioned. The amendment was proposed by Congress on December 9, 1803, and was ratified by the requisite three-fourths of state legislatures on June 15, 1804. The new rules took effect for the 1804 presidential election and have governed all subsequent presidential elections.

Under the original Constitution, each member of the Electoral College cast two electoral votes, with no distinction between electoral votes for president or for vice president. The presidential candidate receiving the greatest number of votes—provided that number was at least a majority of the electors—was elected president, while the presidential candidate receiving the second-most votes was elected vice president. In cases where no individual won the votes of a majority of the electors, as well as in cases where multiple persons won the votes of a majority but tied for the most votes, the House of Representatives would hold a contingent election to select the president. In cases where multiple candidates tied for the second-most votes, the Senate would hold a contingent election to select the vice president. The first four presidential elections were conducted under these rules.

The original system allowed the 1796 and 1800 presidential elections to elect a president and vice-president who were political opponents, constantly acting at cross-purposes. This spurred legislators to amend the presidential election process to require each member of the Electoral College to cast one electoral vote for president and one electoral vote for vice president. Under the new rules, a contingent election is still held by the House of Representatives if no candidate wins the presidential electoral vote of a majority of the electors, but there is no longer any possibility of multiple candidates winning presidential electoral votes from a majority of electors. The Twelfth Amendment also lowered the number of candidates eligible to be selected by the House in a presidential contingent election from five to three, established that the Senate would hold a contingent election for vice president if no candidate won a majority of the vice presidential electoral vote, and provided that no individual constitutionally ineligible to the office of president would be eligible to serve as vice president.