Except the two party system is still an illusion. When support for the three parties is 34%, 34%, 32% then the actual vote will result in 51%, 48% and 1%.. but the second the "real" support passes that threshold you will see an immediate and shart ~50% flip in votes. In other words, the system appears to be two party but it still ultimately will follow the underlying "real support", thus there is no two party system, not really.
This is why every time the parties have switched the new dominant party had ~1% voting support the previous year despite a sudden shift.. this happened 7 out of the 8 times a party has switched.