Third parties offer candidates regularly. Their electoral capability grows stronger, given, among other factors, the clean election law which offers public financing to people and parties who hitherto have not had access to big bucks normally given only to the Democratic and Republican candidates. The voting change I am pointing to is called IRV, Instant Run-off Voting. It works this way. Voters at the polls rank candidates in order of preference rather than just one vote per person.
Voters usually have the option to rank as many or as few candidates as they want.
There is no reason for a voter not to rank additional candidates, as a lower choice will never help to defeat a higher choice. The counting of the votes happens on the night of the election via the help of computers. Ballots of voters who ranked that candidate first then are redistributed to the next choice of candidates from those ballots. If there is still no winner, the candidate who places second to the last is eliminated, and the ballots of voters who ranked that candidate first are then redistributed. If still no candidate has reached a majority, the ballots of the candidate who came in third to last are redistributed.