Labour is promising to abolish within 100 days of taking office the MMP coat-tail rule that enables a minor party electorate MP to bring party list mates into Parliament regardless of the 5 per cent entry threshold.
The joke is that, barring a miracle, there seems little chance of Labour leader David Cunliffe and his Green allies forming a government without the aid of the Mana-Internet "party", whose existence depends on gaming the coat-tail provisions.
And having exploited the system for all it is worth - and spent more than $3 million of internet millionaire Kim Dotcom's cash - to get back into Parliament, it seems unlikely that Hone Harawira and Laila Harre will turn around and vote to end the fun.
The stitch-up between embattled Mana Party leader Mr Harawira and Mr Dotcom, the millionaire refugee from American law enforcement agencies, is not the first attempt to game the MMP rules. It's just the most egregious.
In 1999, in the second MMP election, Labour leader Helen Clark encouraged Labour supporters in Coromandel to support Green candidate Jeanette Fitzsimons to ensure the defeat of the National incumbent and bring in several Green list candidates on her coat-tails.
Ms Fitzsimons narrowly won - but in the end the Greens' party vote just sneaked over the 5 per cent threshhold, entitling them to six seats anyway.
But it's the well-heeled inner Auckland electorate of Epsom that has become the Las Vegas of MMP.
In 2005, it was a total circus, with Labour's Stuart Nash voting for National incumbent Dr Richard Worth and encouraging his supporters to do the same to try to keep out Act leader Rodney Hide.
Not to be outdone, National voters thwarted this tactic and voted for Mr Hide in the hope he would win and drag another Act MP or two in on his coat-tails to provide much-needed allies for National in the House.
Mr Hide won and brought one extra Act MP into the House despite Act receiving only 1.5 per cent of the party vote.
Thanks to this sort of jiggery-pokery, Act has held Epsom and helped prop up National ever since.
In 1986, when the royal commission headed by Justice John Wallace wrote in support of the "mixed member proportional" system of parliamentary representation, they recommended a threshold of 4 per cent before parties without an electorate MP could enter Parliament in proportion to votes received. Parliament increased the threshold to 5 per cent.
The commissioners felt a need to balance the principle of proportionality with the need to ensure that elections delivered effective parliaments and stable government.
They wanted to avoid the instability of parliaments like Israel's and Italy's caused by a proliferation of small parties.
Why the royal commission added the one electorate seat waiver of the threshold rule is unclear. The 2012 Electoral Commission review, which recommended its abolition, says it was "developed in the context of the royal commission's recommendations for Maori representation (which included the abolition of the Maori seats) and was based on the threshold waiver for the Danish minority in the German state of Schleswig-Holstein". It was to ensure fair representation for Maori and, potentially, Pasifika when the Maori seats were abolished, which didn't occur.
"Members of the royal commission told us they have long regarded the one electorate seat threshold as their one mistake," the review said. "In their view there are no good reasons to retain it and it should be abolished."
The Electoral Commission agreed, saying: "The one electorate seat threshold ... runs counter to some of the most fundamental principles of the MMP voting system, including that all votes should be of equal value, the primacy of the party vote in determining election outcomes, and fairness of results."
It enables a few voters in some electorates "to use the electorate vote to significantly influence the make-up of Parliament by helping to bring in list MPs who would not otherwise be elected. This gives these few voters a disproportionate influence and is contrary to what New Zealanders expect of MMP".
The commission feared that because "it undermined these core principles" it would, if retained, "be a considerable on-going risk to public confidence in the legitimacy of our system of MMP".
These fears were well grounded even then, at a time when the backroom deals were at least being done between parties of a similar political flavour.
The recent deal between Mana and the Internet Party enters a totally different realm. Here we have a leftist Maori electorate MP struggling to hang on to his seat creating a temporary alliance with the angry millionaire Mr Dotcom, who is bent on seeking vengeance on Prime Minister John Key.
He has contributed at least $3 million to help Mr Harawira get back into Parliament, so Mr Dotcom's party candidates can slide into the House on the Harawira coat-tails.
It's a travesty which, as the Electoral Commission predicted, threatens public confidence in MMP. Many politicians on the right will welcome that. For all I know, it's their grand plan.
But for those of us who prefer MMP to the old unrepresentative First Past the Post, now would be a good time to start demanding all parties support an end to coat-tailing.