@mc

fptp is first past the post

in parliamentary systems 3rd parties can form governing coalitions

in ranked choice and other voting systems 3rd parties can be stable and viable

but in the usa it's winner take all, thus "first-past-the-post": winner gets everything

the only purpose a 3rd party can perform in our stupid system is to divide one side, and allow the opposing side to win

you can read up on it courtesy of frenchman Maurice Duverger and "Duverger's Law":

https://en.wikipedia.org/wiki/Duverger%27s_law