Without nitpicking the typical coalition details here, I want to consider a more general point. It's somewhat self evidently not a great thing for countries to be swapping systems back and forth dramatically based on margins of a few percent. It's unstable and will inevitably lead to a systemic collapse as the shifts grow greater and greater over time. It's rocking a boat back and forth.
I would go one step further and say that executive power should be dramatically reigned in, and that laws should take an 80% consensus to pass. And laws also have to be renewed every 'x' years with a similarly large consensus, perhaps with a method similar to constitutional amendment to allow for permanent laws. Under such a system you'd absolutely have to collaborate to ever do anything. And I think this would be a very good thing.
Such a system would also completely do away with divide and conquer as a political strategy, which again is also a very good thing - as that's likely one of the biggest causes of instability in the Western world today.
> you'd absolutely have to collaborate to ever do anything
You could also refuse to collaborate to do everything. This would result in an anarchist system where power/money has the ability to do whatever they want without regulatory oversight and the public are unable to vote to give themselves any rights they can't take by force.
I think that's assuming the status quo of horrible divides. In the past many social bills passed with overwhelming bipartisan support. For instance the Pure Food and Drug Act [1], which would lead to the FDA, was passed in 1906 by a 90%+ margin in both the House and Senate. I mean who's going to oppose outlawing mislabeled products? In a country that hasn't been trained to hate 'the other side', basically nobody.
But in modern times a typical social experiment (of which there are a zillion on YouTube) is to describe some policy passed by a President/party but swap the names to 'the other side.' People's response to the policy will invariably sharply shift. People aren't even thinking about what they think is a good idea anymore, but seeing everything through a hyper-partisan lens. That's obviously not conducive to bipartisan acts, pretty much ever.
> and that laws should take an 80% consensus to pass.
I think this is trying to solve the wrong problem. If our concern was that the second the new party gets that 51% margin they suddenly start passing a ton of laws, that would help reign it in. But that's not really what is happening. Congress has become profoundly unproductive in the last few decades. As an example, the last time Congress passed a budget on time, which is the bare minimum of functioning, was in the 1990s. By basically any metric, Congress is becoming less and less capable of passing laws. Requiring 80% consensus would make that even harder. And requiring laws to be reviewed every X years would greatly increase the responsibilities of Congress to keep the government functioning.
It's more about the equilibrium and motivations that this system creates. When everything is decided on a 1% majority, there's no real need to cooperate on anything. If you don't have power now, you probably will in a few years and then you can do whatever you want. So you can just focus on getting reelected in the mean time and vote no on everything until then. This, btw, is exactly what happens - Congress spends most of their time in office simply working on their next election. Term limits would seriously help here.
What you mention about budgets is a good example of this. Neither side wants to cooperate on anything at all. So in the House you get things like one side votes 100% yes, the other side 100% no. And then it gets passed to the Senate. The reason budgets freeze up in the Senate is the filibuster where you need a 60% majority to pass. So suddenly there's actually some cooperation required which is when both sides tend to start working together, a little, to add this or remove that.
But with an 80% consensus required, you need to start the cooperation immediately in the House because you can't just roughshod your fantasy budget through on a 1% margin. And none of this is going to change in 4 years, or 40. If you want to get things done, you need to start viewing 'the other side' as just other people working towards what they see as a desirable direction for the country, instead of an opposing team to be conquered and strawmanned into the worst evil since Hitler.
The party that actively attempts to destroy a government by blocking all bills, then point to the underfunded, broken system and say "government does work, you should sell all of that to a billionaire" would LOVE your idea.
I would go one step further and say that executive power should be dramatically reigned in, and that laws should take an 80% consensus to pass. And laws also have to be renewed every 'x' years with a similarly large consensus, perhaps with a method similar to constitutional amendment to allow for permanent laws. Under such a system you'd absolutely have to collaborate to ever do anything. And I think this would be a very good thing.
Such a system would also completely do away with divide and conquer as a political strategy, which again is also a very good thing - as that's likely one of the biggest causes of instability in the Western world today.