That problem occurs in exactly the same way on any vote in a "normal" parliament where party affiliation determines vote.

> D has a share in "voting weight", but no power at all. We can say this for sure

This is interesting in a different way. D's ability to vote has no power at all. That's true. You're taking a leap when you extrapolate that D has no power; by that argument, lobbyists have no power either. Is that something you believe?

> That problem occurs in exactly the same way on any vote in a "normal" parliament where party affiliation determines vote.

It also occurs under most 'normal' voting systems in safe seats.

Lobbyists have power through money and networks. If a non-pivotal voter has power, it's likewise through something else than his vote.

That this is a problem with party whipping in parliaments too, doesn't mean it's not a problem.

I'm not sure party whipping is actually a problem?

Btw, parties and how they work in specific electoral systems are (at least partially) a function of how general voting works in those systems.

If you have a sortition system, parties might work rather differently, if they would be present at all. MPs submit to the whip's party discipline, because they need the resources of the party to get re-elected etc. Under sortition, the incentives are all different.

Who says parliament has to run by majority vote?

You could run parliament on probabilistic lines, too.

More realistically, I agree with thaumasiotes: this is exactly how forming a government works in most parliamentary systems around the world (eg both in the UK parliament and the German Bundestag.)

> You could run parliament on probabilistic lines, too.

My instinct is that this would have significantly more negative effects, to do with the ease under that system of making radical policy changes.

Though more likely, it would fall into a pathological state where most votes are votes on whether to retake other votes.

Probabilistic doesn't have to mean completely uniformly random.

And you can also still have safeguards, like constitutional guarantees etc.

There may be something to say for small, "moderate" parties being pivotal, having the deciding vote. But that's why I emphasised, this is completely independent of political opinions. D are powerless whether it's a centrist or an extremist. There's no way to defend that as a feature.

Of course, if A, B, C and D are groups of people with less than perfect party discipline, the people in D may still have some power.

What's a small moderate party? Moderate parties are larger than other parties.

No, not necessarily. They may be so bland as to please nobody. (This was the case for an old rural progressive party in my country for many years). Or, they may be neutral by default on most left-right issues because they really care about something mostly orthogonal to it. This has been the case for the Christian Democrats and to a lesser degree the Farmer's party in my country.

The paradox is that they get a good deal of power being pivotal, but only on issues they don't really care so much about.

See the role the Free Democrats https://en.wikipedia.org/wiki/Free_Democratic_Party_(Germany... played in the German Bundestag for a long time.

> D are powerless whether it's a centrist or an extremist.

No. That's only true in a deterministic parliament that works by majority rule.

You could have your parliament make decisions by lot (with probabilities weighted by what MPs vote for).

Or you could give your parliamentarians a steady stream of tokens they could use for voting; small parties could save up their tokens for a while, to have a decisive influence on something they care about.

(You'd have to work out a lot of kinks in such a token system..)