From the start, the New Labour government has been permeated by contrasting cultures. Ideological division is close to zero, though Blairites vs Brownies is a battle sometimes made to stand proxy for factions of the left and right. There is really no such contest.
But there has always been a contrast of tone, of style, of milieu, of social aspiration, between what one might call flash politics and drudge politics. Peter Mandelson's resignation heralds, not to Labour's disadvantage, a decisive victory for the drudgery style.
Tony Blair had undeviating faith in Mr Mandelson's judgment and fraternity. The parting of the ways was necessary, because once too often, and close to an election, Mr Mandelson skated beyond the edge of the truth.
The prime minister has a personal instinct for loyalty, as well as a political desire to offer no scalp to the other side, which he showed in the Commons with repeated recognition of what the now-defunct minister did for Ireland. The end had a pain reaching beyond the normal purlieus of political cynicism.
The departure also marked a cultural shift. Mr Mandelson, though he has other qualities, personifies the flash side of New Labour. He occupied the junction where the new rich met showbusiness and aspiring socialites made their bids to climb aboard the new establishment.
What often got lost in the Mandelsonian images that tend to define the Blair government is how large a proportion of its ministers are, in a drudge-like way, competent.
But the drudges tend to be overshadowed. They're the victims of the presidentialism that puts Tony Blair at the top and the rest nowhere, around which much of the flashiness and all Labour's image-building rotated. That was a style of politics that Mr Mandelson was most influential in inventing when Labour was in opposition. The predominant image of the government - its divisions, its bitcheries, its rivalries, not to mention its apparent obsession with appearance over content - comes from a relentless focus on the lives and work of four men, Mr Blair, Mr Gordon Brown, Mr Mandelson and Mr Alastair Campbell.
Here's where the glamour and excitement are. In terms of plodding competence, this is beginning to show itself as one of the best governments of the last half-century. Yet the flash-dancing gets just about all the attention.
Mr Mandelson's withdrawal will help to change that. His absence won't, on the other hand, make cabinet reshuffling any easier after the election. Yesterday's emergency surgery doesn't diminish Mr Blair's problem which is, unusually, a surfeit rather than a scarcity of talent.
It was never likely that Mr Mandelson would become foreign secretary any time soon, mostly because of the incumbent's burgeoning talents, after early turmoil in his private life, as a brilliant drudge. Replacing Robin Cook with Jack Straw, his plausible rival, would be a Eurosceptic signal the leader won't want to give. So that's one non-vacancy. The Treasury is also unlikely to change hands.
Some see Mr Brown's shift to the Foreign Office as the way to finesse his anti-euro sway at the Treasury, as well as proving Mr Blair's domination. It doesn't make sense. Mr Brown would loathe and fight it.
I regret seeing Mr Mandelson go. He has the breadth and many of the skills our public life always needs. He plainly has incautious judgment when it comes to his own affairs and contacts, but he's right about Europe, being one of the few ministers to give that keynote subject the priority it deserves. He also showed a lot of political guts in trying to progress the peace process.
On the other hand, a distraction has departed. Having helped refashion Labour into an electable party of the centre, he leaves the field to people who are more old Labour in style if not content: decent, earnest, often incredibly dull but the types with whom voters feel more comfortable.