> Isn't it? FPTP makes it all but impossible to sustain a third party because of the vote splitting effect.

I guess it depends how you are using "cause." Is it a causal variable? Sure, I wouldn't push against that. But I want to stress rather that it is a pressure rather than the only contributing variable. That there are more variables with similarly strong pressures, such that by fixing voting we shouldn't expect to have a stable system with multiple parties overnight. Unfortunate as is, things are never that simple. Even more unfortunately, not being transparent about this seems to have the effect of making more progress because people will reframe things as "well we were promised x would fix y, and it didn't, so why should we expect z to be any different?"

But I want to be abundantly clear, I am very in favor of changing to cardinal systems and it is one of the few things I take very seriously when it comes to politics. It is hard to know me and not know about approval and star. You could call me annoying lol. But I want to also make clear that while this is an important step, it isn't the end. It is especially important to remember that democracies are not stable equilibria, but unstable. We will always need to take care and never get lazy. It's unfortunate, but that is the price of freedom. Luckily with most things, effort is low to maintain systems if you are consistent. Unluckily, we're really bad at maintenance and think it is best to fix things when they are problems rather than fixing things before they're broken (a much cheaper solution in money, time, and effort). We've been fooled by "don't fix what ain't broke." That's actually the best time to fix things.

> But these things are related.

I agree. And that's part of an even larger coupled system. The tyranny of coupled systems is that you can't solve the problem by solving one equation at a time. You have to solve them together.

I'll give you an added incentive for cardinal systems that you might not be aware of. They're also REALLY good for analysis. Much better than ordinal actually. Reason being exactly why they are good for voting too actually. It is all about how we embed information. Cardinal (with exception of approval) has the benefit of non-fixed distances being placed upon candidates. While this doesn't have infinite resolution, it can allow us to express how much more we like someone than someone else. You probably know this part but it needed be restated. The analysis part comes down to looking at all these interactions beyond who just wins an election. You have a much better idea about where your voters actual preferences are. You do likely have to end up doing some proxy estimations here (such as most of winning candidate A's voters who did not pick them as their primary candidate picked candidate B. This suggest A should shift more towards B's policy for proper representation! Not only do we pick a better candidate, but we have a clearer picture of where the actual public preference is. This can, and should, be used even down to a regional level to help candidates become the best representatives they can.

BUT like all things, this too can be hacked. You can of course become just enough representative. This might be a helpful video to visualize this issue[0]. I should also add that of course voter preference actually lies along a much higher dimensional manifold than the one we are expressing with any proposed voting system. I don't actually suggest increasing the dimensionality because you have to balance simplicity and transparency. But there is a problem that distances are far more complicated of a subject than many actually like to believe. This is actually at the core of the Curse of Dimensionality (the furthest point becomes more difficult to distinguish from the nearest point, which is why it is generally discussed with kNNs, but generally this isn't always stated or remembered). It's also important to remember that operations may not always be well defined. I am mentioning this because the issue being discussed in [0] can be exploited in any dimension and any distance function we set. This can better illustrate the point I made about unstable equilibria. And you'll notice their suggested defense explicitly depends on the public coming together to act as a coalition and to treat policy setters (government) as an adversary. Which we both have agreed in the past is a core American ideal. It is why I am against labeling and any form of tribalism. But we must admit this is a difficult task, even if it is a core concept of what makes civilization possible in the first place: considering your neighbors. So I just want to always stress that. Don't just consider what is best for you, or for your family. But make sure to always consider those around you, especially those you disagree with, because they are the ones that can be leveraged against you (and you against them!) to have a worse outcome for everyone.

The tyranny of the modern world is that it is complex and interconnected. That we've solved most of the simple problems. So the dangers that are presented to us generally are due to abstraction and complexity. There are not more "first order" (if this then that) problems. And anyone trying to sell you that is either naive or deceiving you. Even if that person is ourselves (it often is).

[0] https://www.youtube.com/watch?v=goQ4ii-zBMw