> Only the presidential elections need to be single-winner.

An interesting thought experiment is having 3 equally powered heads of state (or indeed any small odd numbered group).

Most people's instant reaction is that it wouldn't work because we don't have it now.

After some reflection most people think it wouldn't work for other reasons that they can't adequately explain.

I think if you're going to contemplate nation-state wide administration reform it's worthwhile contemplating all kinds of changes.

(I'm in AU, where we have some semblance of 2pp, though in our most recent federal election some 25% of people did not vote for one of the two major parties/coalitions. Our system is clearly broken, but not as badly as the USA's. Small comfort.)