KEY POINTS:
Calls for a referendum on MMP have been an undercurrent in New Zealand politics since the nation voted to change the first-past-the-post electoral system in 1993.
The chances of a second look at MMP are increasing, with National pledging to hold a referendum if elected. United Future and Act support the call and depending which way the cards fall after the election it could be a distinct possibility.
What National proposes
A two stage, binding referendum, no later than 2011. Although the details are yet to be worked out, it is likely to be similar to the ballot which introduced MMP in 1993.
The first will ask voters if they support the current system. If the answer is no, the second will ask them to choose an alternative.
Why hold one?
National has included a binding referendum in its election policies since 1999.Although National deputy leader Bill English told the Herald's Mood of the Boardroom forum in May last year that his party would not hold a referendum and MMP would stay, it was unveiled as policy again in May this year.
Leader John Key said English's view was a "personal" one.
Key said the decision to include it again this year was not so much a sign of discontent with MMP as "widespread demand" from voters that after 12 years of the system it was time for them to pass a verdict on it.
"There's a very strong feeling from New Zealanders across a wide spectrum that they were going to be offered the opportunity to kick the tyres but they haven't had that opportunity. I don't think that necessarily means they will reject MMP or proportionality. But I do think they feel they are entitled to express a view on it."
Wasn't there a promise to hold a referendum?
It is a myth that New Zealand was promised a further referendum on MMP when it was first introduced. The Electoral Act only required a review by a Parliamentary committee which was to consider whether there should be a referendum.
That committee was only allowed to make recommendations that had near-unanimous consent of the parties involved, and when it reported back in August 2001 there was no such consent on the issue of a referendum.
Otago University electoral law expert Andrew Geddis agrees with Key that the perception voters had of a future referendum had become the political reality.
"On a principled level, there was a widespread belief - and it was a wrong belief - that people were promised a referendum to have another go at it. I think most people felt cheated. Perceptions are just as important as reality in this area."
Will it get the support needed?
Popular legend has it that it will be nigh impossible to secure the majority of support in Parliament needed to secure a binding referendum, primarily because it would require the support of minor parties whose existence depends on MMP.
Act leader Rodney Hide said a referendum should be held "as soon as possible" accusing the other parties who opposed it as acting to protect themselves out of self-interest.
He personally believed FPP was best for the country, although it could mean the end of his party's time in Parliament. At the least, voters should be able to pass judgment on MMP.
Labour, the Greens, Progressives, NZ First, and Maori Party remain opposed, accusing National of self-interest and a yearning to return to the "good old days" of FPP.
Green co-leader Russel Norman echoes comments made by the late Rod Donald - one of the main pro-MMP campaigners for the 1993 referendum before he became the Green Party co-leader: "We don't think people will want to go back to the minority elected dictatorships of the old days."
Prime Minister Helen Clark, asked last week about a referendum replied: "If it's not broken, why fix it?"
Maori Party co-leader Tariana Turia also dismissed Key's proposal as "political game-playing."
"The reality is no-one in the electorate is asking for a referendum. They don't talk about it at all."
NZ First leader Winston Peters - whose party's place does currently depend on MMP because he does not hold an electorate seat - has also been scathing of the proposal, saying Key was simply acting to appease the Business Roundtable.
Key said such criticism was incorrect, saying he preferred some form of proportionality and insisting it was not a sign he was unwilling to work in the MMP environment.
"I think all political parties should think this through carefully before they cut off an opportunity for New Zealanders to have a referendum."
Law specialist Geddis said while neither of the major parties had supported MMP when it was first introduced, Labour had since become "acclimatised" to it.
"National has only had one run at it, and didn't make a particularly good job of it."
Would a "no" for MMP mean a return to first-past-the-post?
Not necessarily. Even MMP's most vocal opponents are now leaning toward some form of proportional representation.
The debate and campaigns in 1993 centred mainly on FPP and MPP - leaving other systems without a look-in. However, there are increasing signs that the Supplementary Member system could be promoted as an option if the public wanted a change.
Key personally is "leaning toward" Supplementary Member under which parties win electorate seats but Parliament is topped up by an extra 20 to 30 seats which are allocated proportionately according to the party vote. In 1992, the option only won 5.6 per cent of support in the referendum trailing behind all other three options.
Arch MMP rival Peter Shirtcliffe expressed support for supplementary voting, which would partly remedy his main gripe against MMP of allowing MPs voted out by their electorates to return to Parliament on the list.
Critic Graeme Hunt has also said he believes New Zealanders are not interested in returning to FPP, but would rather a more diluted version of proportionality than MMP.
Such a change would put more importance on the electorate vote but would not necessarily be the end of smaller parties. Act, United Future, the Progressives and the Maori Party are all in Parliament because of their hold on electorate seats. None polled over the 5 per cent threshold needed to secure places as parties.
However, reducing the number of seats which were allocated proportionate to the vote would diminish the representation and bargaining weight of smaller parties. The major parties would find it easier to secure a majority, reducing the likelihood of multi-party coalitions.
The sticking points
Both Anderton and Norman say there would need to be rules on how much opponents and supporters of different sides of the debate could spend on campaigning.
Norman said the last referendum had seen "the forces of darkness spend millions trying to get the outcome they wanted".
Anderton also said MMP's opponents had "spent bucketloads" promoting their cause.
Then, the anti-MMP brigade included the Campaign for Better Government, founded by Peter Shirtcliffe, and the Business Round Table.
Graeme Hunt - who also opposed MMP and was behind renewed attempts to force a referendum in 2001 - has already indicated he intends to mount a campaign pushing for Key's promised referendum.
Geddis said there was a question of how the arguments on both sides could be balanced. One option was to allow only certain recognised groups to campaign.
He said Quebec's referendum system took this to extremes, allowing only one official campaign for each side of the referendum question. All others were effectively required to stay silent.
Another problem is the phrasing of the questions that would be asked. Anderton said it was critical to ensure it was not loaded either way.
Key said details were yet to be established but he was not opposed to allowing an independent body to draft the questions.
Geddis agrees the wording is critical. "It's easy to get the result you want by the way you ask the questions. You would want it to be drawn up in a way that is as objective and neutral as possible."
HOW WE GOT MMP
* 1986: Royal Commission Report on Electoral System recommends introduction of MMP.
* 1992: September - 84.7 per cent of voters said they wanted a change from FPP in an indicative referendum. The same referendum asked which of four other options voters preferred. 70.5 per cent chose MMP.
* 1993:November - a referendum on election day asking voters to choose between MMP and FPP. MMP won with 53.9 per cent.
* 1996: First MMP election results in National/ NZ First coalition.
THE MECHANICS
Under the Electoral Act, changing the method of voting can only be done by a 75 per cent vote in Parliament, or by a majority of voters in a binding referendum.
To hold a binding referendum, special legislation is required - so National will need a majority in Parliament to get the referendum up.
The only previous example of this being done was in 1993. In that referendum, the law changes required to change to MMP were automatically triggered by the majority vote in the referendum, rather than depending on a subsequent parliamentary vote.
The change to voting methods is one of the rare provisions - known as "reserved provisions" with special protection to ensure voting methods can not be changed by a slim majority in Parliament.
Others include the voting age, the way electorate boundaries are set, the length of Parliamentary term and the make up of the Representation Commission.
National leader John Key proposes to hold the first referendum in time for the 2011 election - which Otago University electoral law expert Andrew Geddis says could be a struggle because of the need to set up the process and run an education campaign.
"If you look at the Electoral Finance Act you can see the problem of trying to rush through that law.
There would be a certain irony if National replicated that state of affairs having spent the past year making Labour's life hell over it."
