What a week.

The Greens embraced the Treasury.

National embraced public transport in Auckland.

And Labour embraced Jane Kelsey.

It is probably not too difficult to see who the winners and who the runners-up are here. National might have been late – really late in fact – to seeing the virtues the central city rail link.

But Prime Minister John Key is nothing if not flexible – to put it politely. If Aucklanders want rail, well, who is Mr Key, keen on a fourth term of office, to stand in their way?

The government might have backed down on the issue, and the backdown might have had all the elegance of shortsighted rhinoceros trying to back a trailer, but, at least, it was a unified backdown.

In sharp contrast, the Labour Party is jackknifing confusingly and messily all over the road over the TPP agreement.

The week closed with Andrew Little looking as though he had lost control of the issue, with two former leaders Phil Goff and David Shearer opposing his opposition to the TPP deal, and with Grant Robertson – Labour’s choice as Finance Minister in any future government – appearing on a platform with tenured university radical and free-trade opponent Professor Jane Kelsey.

The Green Party had a good week. The rail announcement came just a day after the Green party has suggested the Treasury is a bunch of all-round good eggs, and would be just the folks to carry out independent costings of political promises by all political parties.

The Treasury, Green Party co-leader Metiria Turei told NBR Radio earlier this week, has been doing a lot of good work on matters such as inequality and is not necessarily the ideological enemy many people on the political Left believe it is.

While this left a number of people on the political Left spluttering into their decaffeinated soy mochaccinos, it is, it is in fact quite an interesting idea.

Not interesting enough for Mr Key – or perhaps a little too interesting for him. In any case, the last thing Mr Key wants is to have the Greens looking responsible and ready to be included in any government.

But it has to be said that this week the Green party looked like the senior, rather than the junior party of New Zealand's political left wing.