Democracy depends not only on a fair electoral system but on the "legitimacy" of the Government it produces. Legitimacy in this sense has less to do with law than with popular will. The Government's right to hold power must be recognised not just by those who voted for it but, far more importantly, by those who did not.
New Zealand has yet to discover whether MMP can pass that test. The four elections held so far under the proportional system have all produced Governments led by the party that won the most votes, the party that was "first past the post". But sooner or later that will not happen.
At every election we have to contemplate the possibility that the party finishing second past the post might cobble together a coalition with small parties. It could have happened at the last election when National finished just one seat short of Labour. It could happen this time if the gap narrows in the next two weeks and the Maori Party sides with Labour and the Greens.
It would be perfectly in line with the principles of MMP but it is one thing to change electoral law, quite another to change a nation's political culture. Would a government led by a party that "lost" the election be recognised as legitimate?
We put that question this week to a representative panel of eligible voters. Of the 100 who replied, 60 believed New Zealanders would not regard it as the rightful government. Only 20 believed they would accept it, and 20 were unsure.
That sentiment might not surprise political leaders, who tend to be well attuned to the country's political culture. It is no coincidence that all post-election negotiations under MMP have produced Governments led by the first past the post. Small mid-spectrum parties usually undertake to talk first to the party that wins the most votes, and between the major parties there seems to be an acceptance that should happen. Nothing in MMP insists it should happen this way and in many countries with proportional systems there is no such practice.
It is common in those countries for parties that are not the most popular to form Governments opposed by the party with the most votes. But those countries do not have a heritage of Westminster elections in which Government must go to the party with the most votes.
That heritage is hard to shake. New Zealanders still go to the polls with the idea that they are deciding which party will run the country for the next three years. In fact, they are electing a Parliament in which the parties will decide who runs the country. But the Westminster heritage possibly makes the parties more attuned to the voters' choice.
A country's political culture is not static. We adopted MMP by popular vote after a period of economic stress and discontent with democratic accountability of successive single-party Governments. Twice, it needs to be remembered, Labour won the most votes overall but was denied power under the previous system.
There was some grumbling from Labour at the time but it accepted the result and so did the country at large.
Doubtless the discontent would be no more serious now if power went to the second and third parties past the post. But it is clearly not what most voters want or believe should happen. Around 80 per cent of them vote National or Labour and when they go to the polling booth they believe they are choosing a Government. If their party is beaten at the ballot box they accept it is fair and square. Parties trifle with that result at their peril.