Labeen? Grabour? The marriage of the two main parties of the left makes sense, but the course of true love never did run smooth.

Shortly after the Labour Party’s calamitous defeat at the election in 2014, the soon-to-be-former leader David Cunliffe admitted that they had erred in rebuking an offer made by the Green Party, some months before the election, to campaign together.

“I think we can all learn some lessons from history,” he said. “In hindsight the progressive forces of politics probably would have got a better outcome if they’d been better coordinated.”

It may not have made any difference, so hapless was the Labour Party in 2014 – so hapless that MPs in both Labour and the Greens that have told me that it was probably just as well they didn’t get a chance to form a government with NZ First – but it was nevertheless a daft decision.

Essentially, it comes down to this: among those paying any attention, nobody who party votes Labour, and nobody who votes Green, will imagine that either party can take government in an MMP election next year without the other. And if the parties hope to achieve a governing arrangement with NZ First, which, pending some remarkable change in fortunes, they’ll certainly need, they’re much more likely to present a plausible and palatable deal to the public if it’s Labour-Green plus NZ First, rather than a motley and irksome soup of Labour, Green and NZ First.

And so today’s announcement was, if not entirely inevitable, sensible and constructive. It is hardly a massive surprise – except to, for example, one prize-winning blogger, who denounced my April column urging such a deal by saying it proved I did not “understand the basics of politics”, and such a deal was a non-starter, because “trying to get any deal with the Greens is near impossible”.

The Memorandum of Understanding (PDF), in essence, commits to a coordinated approach in the leadup to the 2017 election.

Inevitably there will be tensions, including between the right of the Labour Party and the Green’s carob left. Andrew Little’s advocates routinely argue that the former union leader is a stellar coalition building, an expert at managing disparate teams: that is about to be put to the test. Both parties need to persuade the public that the electoral system was designed to allow coalition governments, and that their arranged marriage is simply behaving – and treating voters – like grown-ups.

Speaking of romance, a high five for this:

And an ew-gross, get-a-caucus-room, for this:

And, of course, players gonna play:

The machinations of political deal-making very often attract the imagery of flirtation, conjugal rites, and the rest.

In that spirit, Little told reporters this afternoon that “this is not a monogamous relationship”. He was making reference to space in the bed for Winston Peters and New Zealand First, of course, but he might be tempting uproar from Family First, because it’s not simply about playing the field, it’s about achieving a kind of polygamy in marriage, uniting in government at least Labour and the Greens and NZ First – maybe more.

That is no easy courtship, and the likeliest outcome less than a year and a half away from the next election remains – at risk of being premature – a National-NZ First consummation. But it is no longer, for Labour and the Greens both, the stuff of fantasy alone.