Interesting. They had some changes in party systems in the US over the course of the country's life, but did they change the voting system?
Britain also had some changes (with labour replacing liberal at the beginning of the 20th century).
I hail from Germany, which traditionally has a more proportional system. (It's a weird mix that seems to do reasonably well in practice. They could replace the first-past-the-post of the `Erststimme' with a score voting system, but the Erststimme isn't that important anyway.) They never had less than three parties in the federal parliament after WWII, even with a 5% threshold needed to move in.
The UK had three somewhat relevant parties in the 20th century (though only two relevant parties per county). Why haven't they changed electoral system? (And when they had a referendum about it, why did they suggest the dreadful IRV?..)
The USA has had changes of party systems, but never in a way that resulted in a lasting third party.
Certainly there are places like the UK, or my homeland, Canada, that have had three relevant parties for a while without changing the system. Although both UK and Canada have forces pushing for reform. The recently elected government of Canada gave an election promise to change the system, but, well, I'm not holding my breath.
But I'm not saying at all that any country with multiple parties will enact voting reform, but statistically, it seems that voting reform is often brought about that way.
I suspect IRV was brought to vote in the UK, because that was deal that could be reached between the Conservatives who didn't want change, and the Liberal Democrats who did. However, I will note that IRV isn't so bad when selecting members of a legislature. Approval/Condorcet elect compromise candidates, but we don't want to simply have a legislature of compromise candidates, but rather representative of how people voted. But some from of proportional system is probably better.
Britain also had some changes (with labour replacing liberal at the beginning of the 20th century).
I hail from Germany, which traditionally has a more proportional system. (It's a weird mix that seems to do reasonably well in practice. They could replace the first-past-the-post of the `Erststimme' with a score voting system, but the Erststimme isn't that important anyway.) They never had less than three parties in the federal parliament after WWII, even with a 5% threshold needed to move in.
The UK had three somewhat relevant parties in the 20th century (though only two relevant parties per county). Why haven't they changed electoral system? (And when they had a referendum about it, why did they suggest the dreadful IRV?..)