We have three parties (plus various fringe odds and ends) here in the UK, but one of them, although it regularly gets a significant share of the vote at national elections, will never make a substantial impact while our voting system remains the way it is.
That leaves two parties. They used to be, effectively, the party of the rich and the party of the proletariat, but now you can't tell them apart.
Though it doesn't stop them arguing about everything, of course.