1972:
Every time Richard Nixon ran for president, one of his electors betrayed him. Roger MacBride of Virginia was a "libertarian" type Republican. He had ran for the Republican nominatoion for Governor of Virginia in 1964. In 1972 MacBride cast his vote for Libertarians John Hospers and Theodora Nathan. This made Ms. Nathan the first woman to win electoral votes. MacBride would be the Libertarian Candidate for President in 1976, but no electors backed him up!
That went into my report on third parties