Alexander Hamilton, writing as Publius in Federalist #68, said that "a small number of persons, selected by their fellow-citizens from the general mass, will be most likely to possess the information and discernment requisite to so complicated an investigation" as to who should be president. However, in practice the electors have never really been expected to excercise their own judgement. In the first two presidential elections George Washington was unopposed. During his eight years at the helm, political parties had grown in power and become the driving force in American politics. By 1796, the first contested presidential election, parties expected their electors to vote as instructed. Today, electors chosen by the parties are usually extremely loyal members who would never consider not voting for their man. In 2000, twenty-six states and DC had laws requiring electors to vote as pledged (see Which electors are bound?). But every once an awhile, the rare "faithless elector" appears and votes contrary to his parties wishes. Only 10 of the 21,358 electoral votes cast between 1789-2000 weren't cast as expected. The faithless electors have different reasons for changing their vote, but they have never changed the expected result of a presidential election.

(This list includes only electoral votes cast for president. Electors voting for someone other than the person they were expected to vote for due to the death of that candidate are not considered here as faithless.)

FAITHLESS ELECTORS
year	elector	supposed to vote for:	actually voted for:
1796	Samuel Miles Pennsylvania	John Adams Federalist	Thomas Jefferson Democratic-Republican
The first contested election also had the first faithless elector. One angry voter writing to the Gazette of the United States said "What! Do I chuse Samuel Miles to determine for me whether John Adams or Thomas Jefferson shall be President? No! I chuse him to act, not to think!"
year	elector	supposed to vote for:	actually voted for:
1820	William Plummer, Sr. New Hampshire	James Monroe Democratic-Republican	John Quincy Adams Democratic-Republican
There are conflicting accounts but Plummer either didn't think anyone but George Washington should get a unanimous electoral victory or he wanted to end the Virginia line of presidents (out of the 5 presidents to this point in history, 4 had been from Virginia).
year	elector	supposed to vote for:	actually voted for:
1948	Preston Parks Tennessee	Harry Truman Democratic	Strom Thurmond States Rights (Dixiecrat)
year	elector	supposed to vote for:	actually voted for:
1956	W.F. Turner Alabama	Adlai Stevenson Democratic	Walter B. Jones
Turner voted for a circuit court judge from his hometown.
year	elector	supposed to vote for:	actually voted for:
1960	Henry D. Irwin Oklahoma	Richard Nixon Republican	Harry F. Byrd Democratic
Irwin was involved in the first known plot to try to sway other electors to change their votes along with him. He had telegramed many of the electors and tried to get them to drop both Nixon and Kennedy, and choose another candidate instead. In the end, he was the only one who didn't vote as bound.
year	elector	supposed to vote for:	actually voted for:
1968	Lloyd W. Bailey North Carolina	Richard Nixon Republican	George Wallace American Independent
Bailey seemed to be a wishy-washy elector who couldn't decide what his reason for voting contrary to his instructions was. First he said he was upset with Nixon's appointments and did it to protest. Then he said it was because his district had voted for Wallace. Then he decided, no it was just a protest vote. Bailey may be one of the reasons that North Carolina now replaces faithless electors before their votes are counted in Congress! (UPDATE: In a December 2000 CNN story, Bailey said he did it because he was upset with Nixon's appointments.)
year	elector	supposed to vote for:	actually voted for:
1972	Roger L. MacBride Virginia	Richard Nixon Republican	John Hospers Libertarian
MacBride, active in Republican politics most of his life, would switch parties and run as the Libertarian candidate for president in 1976. Unfortunately for him, no electors helped him out!
year	elector	supposed to vote for:	actually voted for:
1976	Mike Padden Washington	Gerald Ford Republican	Ronald Reagan Republican
Realizing his vote for Ford wouldn't help, Padden decided to cast his vote for his preferred Republican candidate.
year	elector	supposed to vote for:	actually voted for:
1988	Margarette Leach West Virginia	Michael Dukakis Democratic	Lloyd Bentsen Democratic
Shocked when she learned that electors could vote for whomever they pleased, Leach switched the candidates of the Democratic presidential and vice presidential ticket on her ballot. She asked other Democratic electors to join her protest, but none did.
year	elector	supposed to vote for:	actually voted for:
2000	Barbara Lett-Simmons District of Columbia	Al Gore Democratic	abstained
In an election where considerable effort was made to get Republican electors to break their pledges, it was a Democrat who would do so. Lett-Simmons left her ballot blank as a protest of DC's lack of representation in Congress