Iron_Lynx, 1 year ago

Because:

A: the system is able to elect candidates who win despite only getting a minority of the vote. This problem becomes worse the more parties participate.

B: in order to maximise the chance of an acceptable compromise taking office, very fringe groups must vote for a very mainstream party. Usually that leaves only two parties that make sense.

C: as these parties become the political space, voting for a specific interest can erode support for the nearest main party, guaranteeing a victory for the other main party.

Bonus: D: growing comfortable with their voter base, it is in parties’ interest to grow more radical.

In fact, without McCarthy and the Red Scare, I would find it strange that the American political scene has developed a nationalist “Republican” party and a moderately conservative “Democrat” party. Many more sane parliaments and governments develop their left to be a socialist or labour party.