Nick Cohen has prayed me in aid of his call for Labour to sack Ed Miliband, by arguing that the Labour party is like a failing company, drifting towards failure.

I like the analogy between Labour and the firm, but I'd draw the opposite inference from Nick - that it suggests that changing leader would have little effect.

The analogy works because Labour, like companies has vintage organizational capital. It has a history and corporate culture which governs its behaviour today: it must be a centre-left party just as Marks & Spencer must sell knickers.

But here's the problem. This capital is both a strength and also a source of constraint. Corporate bosses' room for manoeuvre is constrained by groupthink, inside vested interests, corporate technology, bounded knowledge and - of course - market forces. Such constraints imply that leaders often make little difference. Paul Ormerod and Bridget Rosewell have shown (pdf) that corporate extinction is largely unpredictable and Alex Coad has shown that growth is mostly random. These two facts imply that corporate leaders have much less control over their fate than everyone pretends.

Much the same is true of the Labour party. Any leader would face tight constraints, for example:

- Policy options are seriously limited: there are few policies which would satisfy the three criteria of boosting economic growth, increasing equality and being popular.

- Labour is operating in a market for votes where customers are woefully ill-informed and irrational, not least about inequality.

- Any leader would be undermined by the media. If Balls were leader, he'd be presented as a Brownite thug; David Miliband would be an out-of-touch wonk; Andy Burnham too laddish and lacking gravitas. And so on*.

- Labour has ceased to be a mass party, and so is dependent for cash upon either unions or a few rich benefactors.

- The power of the rich, along with the fact that it's just darned difficult for policy-makers to affect long-run growth, greatly limits what Labour could do or say.

Such forces mean that pretty much any Labour leader would look inadequate. This is all the more so because part of Labour's corporate culture is a questionable record in actually picking leaders.

I say all this not so much to agree with Rob that a change of leader is undesireable, but also to raise a question: could it be that we pay too much attention to individuals in politics, and under-rate the many constraints they face?

* Even Jesus Christ wouldn't be a "credible" leader. Imagine if Nick Robinson had been at the Sermon on the Mount. "Blessed are the meek, for they shall inherit the earth" - "It's a core vote strategy and an uncosted promise. The question remains: can Mr Christ engage with middle England?"