Right-wing Labour MPs John Mann, Chris Leslie, and Mike Gapes have rushed to the internet, TV, and the press to score points against Shadow Chancellor John McDonnell.
McDonnell said just before Labour Party conference that Labour would vote for the Tories' "fiscal charter", on the grounds that it has so many loopholes for running deficits that it carries little weight, and voting against it would help the Tories brand Labour as over-spenders.
On Monday 12 October McDonnell, rightly we think, reversed his position and said Labour would vote against the "charter".
Mann, of all people, is now posing as an anti-cuts warrior. He told the BBC, mock-approvingly, that "Jeremy Corbyn was elected on... tackling austerity", and feigned to criticise McDonnell from the left. The same John Mann published a "manifesto" after the May 2015 general election urging Labour to go for a "huge cut in the welfare budget".
Mann now says voting against Osborne is right. Chris Leslie, the right-wing former Shadow Chancellor, plays the other side of the road, saying that to vote against Osborne is extreme and Labour should boldly... abstain.
Getting Labour's newcomers involved and integrated in Constituency Labour Parties and constituency Young Labour groups is urgent: only when they are properly organised in the party structures can they be an effective counterweight to the spoiler right-wing Labour MPs.
There is a twist to this story. The pressure on McDonnell to back Osborne's move to make budget-balancing a legal obligation in normal times came, as far we know, not from the Labour right but from a section of the supposedly Marxist left!
Socialist Action, a small group which nonetheless has influence through people who have wormed their way into backroom jobs, wrote an article (14 September) accusing Corbyn of being at risk of "ultra-leftism".
It urged caution. "The hopelessly confused idea of so called 'Keynesianism, which does not even derive from Keynes, that the key economic policy to deal with recession is to run a budget deficit needs to be thrown out – errors on this help lower the credibility of left wing policies". Decoded: vote with Osborne, or you are "ultra-left".
Since then McDonnell will have had the chance to discuss with competent (though not even specially left-wing) economists like Simon Wren-Lewis, one of his new panel of economic advisers.
As Wren-Lewis has pointed out: "First, [Osborne's new formulation of the 'fiscal charter'] is for the total deficit rather than the current balance, so it puts a squeeze on investment just at a time that investment should be high... Second, even with the get-out clause... the new rule is likely to make the deficit much less of a shock absorber, and so lead to unnecessary volatility in taxes or spending".