@petrillic @kaoudis This is only half true.
A third party candidate did win the presidency once! It can work! The year was 1860, the candidate was Abraham Lincoln, and the party was the Republicans. Yup, the GOP is what a successful third party movement looks like! Yay?
(Note that post-Lincoln the Whigs disintegrated and the system rapidly collapsed back to two parties, because Plurality Voting is a booby trap that •always• leads back to 2 parties. True then. True now.)