Labour should be kicking itself, hard. Wednesday night's rout of Phil Goff by John Key could - with one large proviso - prove to be the defining moment of this election campaign.
That proviso is that the head-to-head debate organised by the Christchurch Press could only be watched online - not on television.
Nevertheless, there has been extensive media coverage of Goff's horror show. What is astonishing is that the Labour leader left himself so exposed on the crucial question of how Labour can claim it is able to fund its spending promises and still get the Budget back into surplus in the same 2014-15 financial year as National.
On Monday, Labour finance spokesman David Cunliffe parried questions by saying variously that the figures were "not far away" and would be released "in the near future".
Labour's election strategists were conscious of the party's vulnerability.
Indeed. And in fact one of those strategists and Labour Party list candidates, Jordan Carter was in overdrive on Twitter last night reassuring the faithful that the figures would stack up. But even left-leaning tweeps were sceptical, suggesting that the horse has bolted.
And Armstrong continues, suggesting that National has played some very clever pool; read on:
When Labour announced its capital gains tax in July, it released an accompanying table showing how much that and other tax changes would affect Government accounts.
Much to National's frustration, the figures (deliberately) offered only a partial picture.
National's lack of success in highlighting the gap may have lulled Labour into a false sense of security.
But Labour was ignoring two things. This is is a bread-and-butter election. National has persuaded people there is no money for any extra spending.
When it comes to getting back into surplus by 2014-15, there will be scepticism that even National would meet what Finance Minister Bill English concedes is a "challenging" target.
The other thing that Labour did not count on was Key. He made little mention of Labour's spending plans during Monday's leaders' debate.
Labour - basking in Goff's performance in that debate - may have thought it could hold off until today, thereby counting on the whole argument getting lost with the arrival of the weekend.
Instead, Key struck on Wednesday night, repeatedly demanding that Goff show him where the money was coming from.
John Key certainly ripped into Phil Goff on Wednesday night after a pretty subdued performance in Monday night's TV One debate. Whether Armstrong's hypothesis of this being tactical from National, or whether it was just a matter of Key seizing the moment is open to speculation, but the momentum of the election campaign changed in that moment.
Labour will release its figures today, but it will be too little too late; the damage was done on Wednesday night and yesterday as even left-leaning blogs such as the Dim Post went feral on Labour. That two credible opinion polls released yesterday showed a yawning gap between the two main parties, and that no fewer that FIVE polls since Sunday have shown National still in a position to govern alone will give Labour no comfort whatsoever.
And as John Armstrong concludes, it begs an important question:
Labour will today argue that National has overestimated some costs, included policies which Labour has not announced and ignored the increased value of the New Zealand Superannuation Fund and the retention of dividends from Labour not partially privatising some state-owned enterprises.
The puzzle is why Goff did not have this information at his fingertips on Wednesday night.
Phil Goff will be wondering that as well. He seems to have been very badly let down by his advisors.