This week was Labour's by a country mile, thanks to Mr Jones' carefully-conceived, astutely-timed and precisely-targeted blitzkrieg-style offensive against Countdown, the Australian-owned supermarket chain.
In the space of just a few minutes in Parliament on Wednesday afternoon, Mr Jones made an extremely serious allegation regarding Countdown's business practices. In doing so, he also entrenched Labour as the White Knight on the front line of the Supermarket Wars.
It is all about repositioning Labour more firmly in voters' minds as the consumer's friend who will confront big business greed rather than being a corporate lapdog like National. It is about ensuring the economic debate at this year's election concentrates on prices, wages, income inequality and child poverty - not economic growth forecasts, budget surpluses and debt repayment, where National has a huge advantage.
Mr Jones' virtuoso solo performance was but one episode in yet another extraordinary week in New Zealand politics. The week also witnessed behaviour varying from the simply bizarre - the Prime Minister confirming he is not a ''reptilian alien'' - to the constitutionally stupid - Greens co-leader Russel Norman revealing his party would probably veto any order made by the courts to extradite Kim Dotcom to the United States - to the plain silly - Winston Peters insisting he has been placed under surveillance by the Security Intelligence Service.
In fact, it could have been the perfect week for Labour, had David Cunliffe not wasted an opportunity to nail the Greens to the wall, thereby making it very clear to the public who is going to be the boss in any Labour-Greens coalition government.
Mr Norman's musing aloud on the Greens' stance on Mr Dotcom's fight against extradition was a major gaffe.
The Greens seem to believe that the wide discretion that the law gives to the Minister of Justice amounts to carte blanche for the minister to pick and and choose who goes and who stays.
That discretion in the law is obviously there to deal with any anomalies or unforeseen circumstances.
Mr Norman's mistake was to talk about blocking Mr Dotcom's extradition if given the chance, while in almost the same breath referring to Mr Dotcom not going ahead with the launch of his Internet Party, which would have dragged votes off the Greens and other left-leaning parties.
Mr Norman might argue that he was talking about two very different things.
But it was inevitable Mr Key would link them and declare the Greens, who have attacked National's electoral accommodations with minor parties, were about to strike a far more dodgy one of their own.
Mr Norman can rightly argue that at least he had been open about his meetings with Mr Dotcom. At times, the Greens pay a price for such transparency.
Mr Norman's embarrassment, however, is a timely wake-up call for a party that can guarantee, with the forthcoming election its best chance yet of making it into Government, that every word uttered by its leaders and MPs will be scrutinised for inconsistency, and where at all possible, deliberately misinterpreted.
Mr Peters does not have that problem, as he is the only person in New Zealand First who is allowed to talk to the media. He remained silent about his Dotcom meetings - at least until Mr Key stirred the pot and wound up Mr Peters' paranoia levels by telling him how many he had held with the giant German.
Mr Peters' subsequent press statement asking how Mr Key had become aware of that figure and suggesting he (Mr Peters) was now being monitored by the intelligence agencies looked like a fit of pique for Mr Key getting one over him.
At the end of the day, why would the SIS be bothered with bugging him?
Unless, of course, Mr Peters has plans to join the Syrian rebels to try to oust the Assad regime. Mr Key confirmed on Monday such recruitment was being monitored by the spooks.
Much of all this was rightly overshadowed by Mr Jones' ripsnorter of a speech, which lashed Countdown for allegedly mistreating the company's New Zealand-based suppliers by demanding suppliers make special retrospective payments for past losses suffered by the company, with the threat of their products being kept off the shelves of Countdown's 200-plus supermarkets in New Zealand.
It is the habit of Opposition parties to call for an inquiry when something goes wrong or things are seen to be seriously amiss. The habit of governing parties is to ignore those calls unless things are so serious or the public so incensed that one cannot be avoided.
A measure of Mr Jones' success was that by Thursday lunchtime - less than 24 hours after he spoke in the House - Mr Key could see which way public opinion was shifting in response. It was trademark Key behaviour - agree to hold an inquiry and thus get the matter off the front pages. as swiftly as possible.
The Commerce Commission got the message. By the end of the day it had announced it had received a complaint from Mr Jones and outlined what steps it would take to ascertain whether Countdown has been in breach of the Commerce Act.
Countdown has ''categorically'' rejected Mr Jones' allegations. It has promised to co-operate fully with the Commerce Commission investigation. Those assurances will do little to help it win the public relations battle.
There is already public indignation that Countdown is party to the ''Buy Australian'' which has forced some New Zealand products off supermarket shelves across the Tasman.
Mr Key had raised that the week before during his talks with Tony Abbot, his Australian counterpart, but got nowhere. It was Mr Jones who provided the retaliation which has otherwise been limited to scattered informal customer boycotts of Countdown stores.
Patriotism may be the last refuge of the scoundrel, but no New Zealand politician has ever lost votes in criticising the diggers over the ditch.
- John Armstrong is the political correspondent for The New Zealand Herald.