A third party running against two polarizing candidates is a pathological case (as are two polarizing candidates alone). IRV gets better when there are more ca

A third party running against two polarizing candidates is a pathological case (as are two polarizing candidates alone). IRV gets better when there are more candidates, because they can form alliances and trade preferences. It goes further than that by /encouraging/ new candidates too because they can align themselves with other candidates and band together against competition. FPTP voting doesn’t encourage new candidates, because they’re competing against the big two. That’s why American politics sucks so much, both in its staleness and how the opponents treat each other.