Which of the following is NOT true of the presidential election of 1800?
a. Thomas Jefferson’s victory in the New England states proved to be key to his election.
b. The importance of slavery and the three-fifths compromise was demonstrated: without slaves counted as part of the South’s population, Thomas Jefferson would have lost.
c. The controversy surrounding who would be president led to the passage of the Twelfth Amendment, which changed the operation of the electoral college.
d. John Adams’s acceptance of defeat established the precedent of the peaceful transfer of power in the United States.
e. The election demonstrated the importance of mobilizing large numbers of voters with more modern campaign techniques, which the Republicans effectively employed.

The 1800 presidential election was contested between Thomas Jefferson, running for the Democratic-Republican Party, and John Adams, of the Federalist Party. Jefferson defeated the incumbent Adams in a hotly contested election, which in the end had to be decided by a ballotage in the House of Representatives, as Jefferson and his running mate Aaron Burr had obtained the same number of electoral votes (73). In the end, after 36 ballots, Congress voted 10-4 for Jefferson, and he was proclaimed as the third president of the United States.

In this question, "Jefferson’s victory in the New England states proved to be key to his election" is not true, because in reality, these states were won by John Adams. The other options are true: as a result of the Three-Fifths Compromise (which counted 3 out of every 5 slaves as part of a state population), southern states received a proportionally larger number of electoral votes than if slaves hadn't been counted at all. The Twelfth Amendment was passed on 1804 to prevent a repeat of the Jefferson-Burr dispute detailed above. The previous presidential elections had been extremely fierce, but Adams took the defeat and moved on. And finally, during this election, mobilization of voters had a major effect not seen before. New York was won by the Democratic Party in great part thanks to the campaign efforts led by Burr.