1796 United States presidential election
The 1796 presidential election was between Federalist John Adams and Democratic-Republican Thomas Jefferson. It was the first election where there was competition for the presidency. Adams and Jefferson became political enemies. However, because it used to be that the second place person would be vice president, it caused Jefferson to awkwardly be Adams' vice president for four years. It would be the reason why the Twelfth Amendment to the United States Constitution was passed later.