Political capital really is like personal capital in that it can grow and shrink.  George Osborne lost a bit of it when he shelved pension reform pre-Budget, and quite a bit earlier when he ditched tax credit savings last autumn.  His mother of all differences with Iain Duncan Smith has lost him more still.

Contrast the Chancellor’s balance in the political bank with Stephen Crabb’s.  The new Work and Pensions Secretary has been quietly building his reputation in Wales, where he helped to gain the Party seats last May.  David Cameron and Osborne needed him to escape from the Personal Indepence Payment imbroglio.  The promotion represented a further uptick on his account.

And so it is that Crabb was able to announce yesterday not only that the PIP savings have been shelved, but that there will be no compensating reductions elsewhere in the Work and Pensions budget.  (Well, strictly speaking the formal position is that there are no plans for such savings, but the practical effect appears to be the same.)  So there’s now a hole in Osborne’s Budget bucket worth £4.4 billion.

ConservativeHome readers scarcely need me to point out that if this accomodation had been reached last week, Iain Duncan Smith wouldn’t have felt he had to resign in the first place.  The whole business has had all the rationality of a complimentary exchange between Arsenal and Spurs fans before a particularly tasty derby.

There have been jokes in the press about crabs moving sideways but this one moving upwards.  Yesterday, he inched forwards.  This Remain-backing-social-justice-supporting-son-of-a-single-mum-raised-in-a-council house has acted from a position of strength.  There is a Crab the dog in Two Gentlemen of Verona who joins “three or four gentlemanlike dogs under the duke’s table”.  The Work and Pensions Secretary may identity with this canine figure.

“He had not been there a pissing while,” says his owner, “but all the chamber smelt him”.  I will lower the tone further by pointing out that Crabb is not outside the tent pissing in but inside the tent pissing out.  In this respect as in some others, his position is different from his predecessor’s.

It sometimes happens after a family row that no-one can remember afterwards what it was all about.  That might just be the position now – despite the loss of a former Party leader and reforming Cabinet Minister – were it not for the interplay between policy differences, a small Commons majority and the EU referendum.  Cameron should send for Michael Gove to help steady the ship, but will instead negotiate the iceberg-laden waters as before, or try to.

Who was right and who was wrong?  I have a lot of sympathy for Duncan Smith over the way what was done was done, but some too for Osborne because what was done needed to be done – or something like it, anyway.  There is no case for simply letting the PIP budget rip.  Of course, when I say what was done, I mean what now will not be done.  It is no use supporting deficit reduction on paper but opposing every plan to reduce it in practice.