The direction David Cunliffe is taking Labour makes even the loosest arrangement well nigh impossible. National, on the other hand, may need Dunne's vote more than ever to stay on the Government benches, especially if the Maori Party returns to Parliament in depleted numbers.
Dunne, no doubt, would like nothing better than to shut Winston Peters out of power, along with other Opposition figures who have tormented him during what has been his year from hell.
Peters kicked things off, accusing Dunne of leaking the Kitteridge report on the GCSB. Dunne was then struck by "several trains coming from different directions at once": the Henry inquiry into the leak, his resignation as a minister, the fuss over his exchanges with press gallery journalist Andrea Vance, the Electoral Commission deregistering his party and the resulting loss of thousands of dollars in parliamentary funding for party leaders like him.
Dunne admits his confidence took a "huge hit" and he even briefly contemplated quitting politics altogether. However, the messages of support and encouragement inside and outside his electorate persuaded him to stay and stand again.
That decision has at least avoided this weekend's United Future conference being a funeral wake.
It's thought unlikely the half-day conference, expected to be attended by around 40 members, will dwell on the leader's faux pas - even in closed session . The unfortunate series of events has already been widely canvassed at party meetings around the country. Dunne will offer his thanks for the party's support in difficult times. But he is not in a mood to offer anyone an apology.
How many electorate votes for Dunne have gone down the gurgler is anyone's guess. He can probably count on it being in the hundreds rather than the thousands. But that would be enough to make things tight, especially as Labour can be expected to do better in 2014 than in 2011.
Dunne has a majority of just under 1400 votes - way down on the 12,500-plus he secured in United Future's heyday in 2002.
Although time will dim voters' recollection of his recent folly, his prime worry must be that he's handed those who have tired of his lengthy tenure an excuse to turf him out.
At the end of the day, however, none of Dunne's constituents have suffered from his behaviour. No crime has been committed - unless you believe leaking a supposedly confidential government document falls into that category
The only victims have been Dunne and Vance. He insists he did not leak the report to Vance. No one believes him. His credibility has suffered accordingly but is nowhere near being destroyed. It will take a lot more than one silly mistake to leave his reputation irrevocably stained.
The upshot is that Dunne is even more dependent on National to help him hold his seat. He has already issued a plea for help in the form of a challenge to National to "nurture its credible partners" - United Future, Act and the Maori Party - over the coming 12 months rather than gifting a seat to "doctrinaire, inflexible, inexperienced extremists" in the shape of Colin Craig's Conservatives. Otherwise, he warns, for National it could be a question of what might have been on election night.
In 2011, National stood a candidate in Ohariu, but took the line that its supporters should give National their party vote and make their own judgment about how to cast their electorate vote.
That was a pretty weak hint to vote for Dunne, and its impact was further diluted by the National candidate Katrina Shanks deciding to campaign hard in the seat, thereby splitting the centre-right vote and nearly handing victory to Labour's Charles Chauvel.
Had the Greens not stood, Chauvel might have just managed to get enough votes to secure the seat. Chauvel, who was already a list MP, has since left for the United Nations in New York. Shanks, also a list MP, announced this week she too was retiring from politics.
There may be some relief within National at that development. While the party may not go as far as not standing a candidate in Ohariu, there is a growing view that electoral accommodations should be spelled out far more explicitly for voters' benefit, rather than hoping they will make the correct choice by gently reminding them with symbolic tea parties and so forth.
With Shanks no longer seeking nomination, National can select someone more willing to put the party's wider interest first by keeping his or her head down and concentrate on building National's party vote.
On the other side of the political ledger, Labour and the Greens similarly have to stop ignoring the political reality staring them in the face. If the centre-left wants to win the seat, only Labour can do it. The Greens should not stand a candidate. And, to be blunt, neither should National in what is a special case.
