Seven weeks out, it's a one-horse race

National starts the election campaign on the best possible foot - with a massive lead and the promise of a rout.

On today's Fairfax Media-Nielsen poll results, National would govern alone.

But strategists are talking down the polls just seven weeks from election day, and say it will be hard for National to win enough support to govern, let alone alone.

Party deputy Bill English said yesterday a win of 50 per cent plus was considered "unlikely" - and history is on his side. No party has won an election with more than 41.3 per cent support under MMP.

If National had less than 45 per cent it might need to look beyond the obvious allies, ACT and United Future, to govern - and after ruling out NZ First, the Maori Party is the most likely option.

The Green Party has not ruled out a deal with National - though as the business end of the election campaign approaches, it remains an unlikely prospect.

But as it eyes up the prospects of holding a more pivotal role post-election, the Green Party has identified three key portfolios - transport, energy and, more controversially, agriculture - as possible bargaining chips.

The Maori Party has been careful to keep its door open to both Labour and National - and co-leader Tariana Turia says it would be wrong to head into the campaign ruling either of them out.

In an indication of the potential powerbroker role held by the Maori Party after the election, Helen Clark and John Key have both been careful to nurture a relationship with the minor party.

But it is still thrashing out what sort of role it might hold in a future government - the options run from staying on the cross benches, to a role similar to that held by NZ First, which secured a ministerial portfolio, but remained outside government.

A more formal coalition would also be in the mix.

The Maori Party is clear, however, that what will drive its decision is recognition of its founding principles and constitution, which include mutual respect, Maori self-determination and the ability to have real influence over key policy areas.

"There is no doubt that what we are considering is where will we get the most influence without having to give up our independence," Mrs Turia said.

The Maori affairs portfolio has been touted by commentators, but education and health were likely to be higher on the party's list of priorities. "We're not even talking Maori Affairs ... It's very limiting."