The argument is on substance, not style

August is a wicked month in the Labour Party. Last year it was Richard Burden, an unheard-of backbench MP who burst from obscurity to denounce the holidaying Tony Blair as a Stalin in the making. This year it looks a little more serious. Clare Short is not obscure, she is not a backbencher, and she is not totally on her own.

Her reaction to her demotion is totally human. But she had it coming. It is almost impossible not to be a little sentimental about Ms Short. She has blood in her veins. She cannot easily be demonised. The engaging and unusually direct connection between her mouth and brain distinguishes her from many other, greyer politicians.

But it is not really defensible in a democracy, in the television age, for a transport spokeswoman preparing for power, to walk out of a studio because she is asked a question in an interview about the strike on the London Underground. Mr Blair had no alternative but to move her. For a leader who Ms Short worried aloud is becoming too much of a "macho man", the Labour leader has shown remarkable forbearance by resisting the temptation to punish her further.

For we should not fall for the old trick of thinking this was really about the spin doctors, fixers and "advisers" around Mr Blair. It is nice to shoot the messenger, but this is about the message. No modern political party in the Anglo-Saxon world, as Ms Short must know, can win power without its share of Mandelsons and Campbells. But when she complains that Labour is "modifying everything we stand for, pruning it down and down and down to be acceptable to the Daily Mail" it's Mr Blair's strategy she's talking about. She is attacking his politics, not just its presentation.

And she is tapping into an incipient internal Labour alienation which goes a little wider than the awkward squad.

There was quite a lot of end-of-term scratchiness among MPs, first about the suddenness of the change on Scottish devolution and then about some heavy briefing against party dissidents. In their heads the majority of MPs applaud Mr Blair's achievement in making Labour represent the majority against the privileged minority, instead of only the dispossessed minority against the majority. But in their hearts, even some loyalists fret that the urban poor might get forgotten in the rush to win over middle England.

When it is so obvious that internal division is the one factor which could lose the election, Mr Blair is right to discipline his party. The electorate punish disunity in Labour as remorselessly as in the Tory party.

It is also laughable to think that he will abandon modernisation because the going is tough. But he also needs to leave October's party conference having re-engaged the body with the head, and having reinforced the image of the "fresh young, principled leader" Ms Short talks about. He has been much better than many of his predecessors in explaining, arguing, persuading that his cause is right. He needs to do even more, especially with MPs. He did it before, with Clause IV:he must do it again this autumn.