Killing the two party duopoly requires significant constitutional changes to how elections are held. One way to do that would be ranked choice voting as implemented in e.g. Maine (https://en.wikipedia.org/wiki/Ranked-choice_voting_in_the_Un...).

However, the key point is that such a system would mainly benefit a potential third party, but any changes to the system need to be agreed upon by the current representatives whose interests and reelection would be hurt by such a change.

Trudeau lost my vote by not going for this in canada, but the problems did hilight that there's a lot of alternatives and choosing a specific replacement is hard.

Most agree that FPTP is bad, but nobody agrees on what to replace it with

Just pick a major one, they're all good in similar ways.

From the perspective of a European outsider, I very much agree. A lot of problems seem to stem from the two party system.

I'm just wondering if there is a good way for a strong third (and fourth and fifth...) party to form under the current system? Are there any good examples from other countries making that transition, and can they be applied in the US as well?

New Zealand switched from a mostly 2 party first past the post system to a proportional multiparty (usually) coalition system about 25 years ago. We would also end up with governments that won the most seats but lost the popular vote.

IMO we have had much better quality governments since from either end of the spectrum. We had a notorious populist authoritarian in the 70s and early 80s, and I don't see those days coming back.

In a "First past the post" electoral system, It's always more advantageous for the 3rd party to merge with the first or second party.

New Zealand changed away from First Past the Post to Mixed Member Proportional in order to fix that

https://en.wikipedia.org/wiki/Mixed-member_proportional_repr...

https://en.wikipedia.org/wiki/Electoral_system_of_New_Zealan...

I'm not sure how you'd implement it, particularly at the senate level.

The current system is game-theory-stable given the conditions of the USA structure of first-past-the-post. You can look at the historical third parties in USA - a third party can form and gain power (with great difficulty) but then it pretty much immediately displaces one of the two parties, so you're back to a two-party system just with different two parties.

> From the perspective of a European outsider, I very much agree. A lot of problems seem to stem from the two party system.

I used to think the same way, but many (most?) countries in Europe end up having coalitions anyway, so you end up really having just two blocks. More parties might give you the option to choose a party that is more after your taste, but in reality you (often) end up with coalitions that take most ideas from the strongest party within the coalition.

I would assume the same thing would happen within the Democratic/Republican Party in the States as well, i.e. a compromise between the left/right wings within these parties based on what is shared by most members(?)

Not really. The blocks change, especially in close elections without true winners. Then negotiations happen and smaller parties often make concessions on the grand scheme of things to get their key issues through.

So, much more compromise than division. This comes back to the voters also. On every divisive topic you have a number of viewpoints instead of two polar opposites.

The issue with that is that you can end up with ineffective 'rainbow coalition' governments. It can also give Independents far too much power since they can threaten to collapse a coalition at any time.

Duverger's law has a lot of redundancy in our current system. If you implement something like IRV on the state level for presidential elections without handling the Electoral College, then you've just further increased the odds of Republican presidencies.

Why Republican presidencies?

Good question. Because it will increase the probability of Electoral Votes going to third parties. That decreases the probability of any candidate reaching an outright majority of Electoral Votes. A plurality of Electoral Votes is not enough; it has to be a majority.

Without a majority, the election is decided by the House of Representatives, where each state delegation gets one vote, where each vote is determined by a majority of that state's delegation.

And there, the Republicans have a built-in advantage similar to their Senate advantage, as every state is guaranteed at least one representative regardless of population. Even after the Democratic House victory in 2018, Republicans still had the majority of 26 state federal delegations.