The election of the 1800 was the one which saw Thomas Jefferson become president. This was possible due to some specific reasons: the electoral system, Burr not refusing a possible presidency and several votings by the House of Representatives.
The electoral system was designed before organized parties became popular in the US.
When both Burr and Jefferson got the same amount of electoral votes -73 each- the members of the House of Representatives had to decide who was going to become president.
Burr was asked during the campaign what he would do in case of a tie, and he responded that he wouldn't stand on Jefferson's way. Nevertheless, when the tie happened, Burr said he wouldn't turn down presidency if the House decided he was going to be the next president.
In order to win, Jefferson needed the vote of the majority of all the state delegations. There were 16 States back then, so he needed 9 to win. After 34 rounds of voting, Jefferson always came up with 8 states, until Rep. James Bayard -from Delaware- voted for Jefferson.
Finally, Jefferson became president and Burr became vice-president, and the Constitution was also amended to prevent a problem like this from happening in the future.
