@freemo @cobratbq "the 2 dominate parties have been replaced 8 times" – sure, but it was pretty much always 2 parties.
Is anyone arguing that it always and forever must be the two parties we have currently?
I think the claim usually made is that structurally the only stable thing is 2 main parties, and they'll morph as needed to always be ~half the country. There can be (*very* temporary) disruptions like a third party that e.g. replaces one of the others, or a party can change wildly (like Dems mid-1900s) etc.