Blink once for new government

There is no constitutional convention which requires minor parties to back the biggest vote winner after an election, despite the positions of New Zealand First and United Future.

Instead, political scientists predict if a tight race produces a hung Parliament after Saturday's election it may come down to one of the minor parties "blinking" on a confidence vote, and abstaining to avoid a fresh election.

There is also the prospect of an overhang of seats caused by parties with a very strong electorate base, and low party vote ratings. This could result in a Parliament of more than 120 MPs and would slightly favour the centre-left bloc, led by Helen Clark and Labour.

The conventions around forming a government and coalition building were spelled out before New Zealand's first MMP election in 1996 by then Governor-General, Sir Michael Hardie Boys, and are simple.

Politicians alone thrash out who will govern. The most significant rule is that whoever governs is the party or group of parties which commands the confidence of Parliament.

The Governor-General, Dame Silvia Cartwright, is only likely to become involved if negotiations stall, or become protracted, and her role would only be that of a facilitator.

Although New Zealand First leader Winston Peters said last week there was a constitutional convention that a minor party offered its support first to the party which won the most seats, experts said that was a political decision and not a convention.

The key was which party could win a confidence vote in Parliament, and that came down to MP numbers.

Jonathan Boston, professor of public policy at Victoria University, said conventions were not based around what was politically acceptable, but what was constitutionally required. "And the very simple straightforward requirement of this context is, to take office as a government, a party or a group of parties must be able to demonstrate they have confidence in the House of Representatives."

Constitutional expert and former prime minister Sir Geoffrey Palmer said: "As the Australians say, 'the first rule of politics is to learn how to count'.

"This isn't technical."

Sir Michael said confidence could be demonstrated through explicit coalition arrangements, a public statement outlining party positions or by winning a confidence vote in Parliament.

According to the latest Herald-DigiPoll survey, both Labour and National would get 50 seats in the election, and a centre-left bloc of Labour, the Greens and Progressives could get to 58 seats.

Expected support from the Maori Party's likely three or more MPs would be vital, especially if there was an overhang and more than 120 MPs.

National, United Future and New Zealand First could get to 60.

In a hung Parliament, without an overhang and with both blocs at 60-60, Professor Boston said one or more minor party might have to abstain on a confidence vote or force a fresh election because no grouping could command the confidence of Parliament and govern.

"My gut feeling in those circumstances is United Future would blink because they've committed themselves to being responsible, they've committed themselves to using their position to ensure stability."

New Zealand First could also choose to abstain to avoid another election, which would also deliver a centre-left coalition.

"Abstention is enough, that's all it would require,"Professor Boston said.

"It looks if there is an overhang, it would be to the centre-left's advantage,"

Ground rules

* Politicians, not the Governor-General, decide who will govern.

* It will be the party or parties which can win the confidence of Parliament; that could be gained through a vote, or through formal agreements.

* Helen Clark will remain caretaker prime minister after Saturday night; convention requires her to resign if it becomes clear she cannot win a confidence vote.

* If no group can command confidence, there will be another election.