[int_19h]

The problem is that the side that organizes always wins over the side that does not. And it's very difficult to ban political organization (which is ultimately what parties are) in a way that is actually enforceable.

The American founding fathers were mostly of the opinion that political parties are bad and should be avoided if republic is to stand. Yet they found themselves organizing into parties before the ink was dry.

So the best we can do in practice is engineer the political system such that the damage from party groupthink is minimal.

[eucyclos]

This is all true, but I think the issue is upstream of where you're pointing - democracy declines when the goal becomes to win rather than to serve the constituents. Parties are a way to win and they also reinforce the idea that winning is the goal.

I'm not sure as to solutions but I don't think they're impossible - something like an inoculation of the entire political class against the memeset that prioritizes winning over serving the constituents. Then if an unofficial party tries to seize power in a system that officially disallows them, the majority is already primed to respond in an organized way.