With just five days of campaigning to go Labour is still trailing National by a significant margin and a change of government is the most likely outcome on Saturday.

It isn't a sure thing by any means, but Labour's chances of winning a fourth term rest on a last-minute swing against National or Helen Clark's ability to stitch together a majority with minor parties.

Last week NZPA's rolling poll, which averages the results of six published surveys, showed National on 47.9 percent support and Labour on 35.2 percent, a gap of 12.7 points which Labour, despite its best efforts, has not been able to turn around.

That's 61 seats against 44 in what could be a 124-seat Parliament because of the overhang expected to be caused by the Maori Party's results.

With ACT in line for at least two seats and Peter Dunne backing National, the centre-right's total goes up to 64.

Labour's ally the Greens have been gaining ground and would win nine seats on the latest poll results and Jim Anderton is expected to retain Wigram -- a centre-left total of 54, still well short of National's tally.

New Zealand First is the wild card. On 2.9 percent of the party vote, NZ First wouldn't get back into Parliament unless Winston Peters wins Tauranga.

If he does, helped by tactical voting from Labour supporters, or the party can get over the 5 percent threshold, Labour could draw together enough seats to leave the Maori Party holding the balance of power.

But Labour's bottom line problem is that it hasn't been able to whittle down National's lead to the point where it can mount a confident challenge.

And it doesn't have much time left.

Labour's hopes of closing the gap rest mainly on two leaders debates on TV this week, Clark's vigorous campaigning and the possibility that undecided voters will swing strongly to Labour when they reach the booths.

In the campaign's closing stages Labour is working hard to persuade voters that with tough times ahead this isn't the time to change the government.

Clark and Finance Minister Michael Cullen are putting a lot of effort into this to show they are dealing with potential problems caused by the international financial crisis.

On Saturday they announced a deal with the big banks that will help people manage their mortgages and avoid forced sales. It could gain votes as mortgage holders nervously anticipate the economic downturn and the possibility of losing their jobs.

National's leader, John Key, didn't miss out on that and was talking about the need for it before the announcement.

And while Labour looks ahead to forging deals with minor parties, National has been doing the same with ACT.

On Saturday Key and ACT's Rodney Hide formalised their post-election arrangement at a get-together in Auckland, and ACT is assured of a role in a National-led government.

Key is carefully avoiding specific commitments, and part of the reason for that is the presence of Sir Roger Douglas as ACT's third list candidate.

ACT needs only a small gain on its 2005 election result to get three MPs -- it had two in the last Parliament -- and Labour is playing up the prospect of a National-ACT government with Sir Roger in it.

Key has been forced to counter that by saying there is no way he will have Sir Roger in cabinet.

Compared with Labour's potentially messy arrangement which rests on support from the Greens and NZ First, with at least the compliance of the Maori Party, National's post-election scenario is comparatively clean and it hopes voters will consider that on Saturday.

Of all the parties, the most messy is NZ First.

Peters is running a strong campaign targeting older voters, based on familiar warnings about the danger of foreigners owning most of New Zealand.

But he is insisting he can work with either of the main parties, which seems ridiculous in the face of Key's repeated statements that he won't have anything to do with NZ First after the election.

Key has had to say this numerous times during the campaign and he is now so firmly on the record it seems impossible that he would change his position even if it meant staying in opposition.

He has, in fact, said he would stay in opposition rather than strike a deal with NZ First.

Key thinks Peters is deliberately misleading NZ First supporters by trying to give the impression he will be a player in a National-led government.

There is, however, one way Peters could have a role. In the unlikely event of NZ First holding the balance of power, he could say his party would abstain on confidence votes if doing that allowed National to command a majority in Parliament.

Key can't stop him doing that, but he would run close to breaking his word if NZ First wanted to negotiate something in return.

But NZ First might not even be there after the election, and if it isn't National's path to power will become a lot easier.