Key Points:

Apparently one out of four voters intends to split their two votes next Saturday. Some voters are starting to understand that they can use their votes strategically to help get the electoral outcome they want.

There is little doubt that National will beat Labour in the total votes cast this election. But despite National's poll dominance, it's unlikely it will reach the 50 per cent mark it needs to rule in its own right.

Even with Act and United Future, there is a possibility that National could fail if its opponents voted strategically.

Helen Clark will try to close the gap between Labour and National. Whatever happens she will rely on the support of the minor parties. People ask me how they can use their two votes strategically to keep a left-leaning government. The following is my advice.

Centre-left voters

Staunch Labour voters will give their electorate and party vote to Labour. But the softer centre-left voters should give their party vote to the Greens.

The Green Party will easily get over the 5 per cent threshold. The Greens are better than Labour on every issue concerning the environment or workers' rights. The more votes the Greens get, the stronger its policies will be in a Labour-led government.

Staunch left voters

There will be a temptation for these voters to give their party vote to openly left-wing parties, such as RAM (Residents Action Movement), the Workers Party and the Alliance (my old party). The combined party vote of these left-wing parties will be less than 2 per cent. That will mean all their party votes they get will be allocated proportionately to other parties that make it into parliament.

Interestingly, that means that half of the staunch left vote will be added to National. If these left-wingers instead gave their party vote to the Greens it would give them another two MPs they wouldn't otherwise get.

New Zealand First supporters

It will take a miracle now for NZ First to get over the 5 per cent threshold given what's happened to Winston Peters. Any of NZ First's soft supporters should now probably throw their party vote to Labour.

The only glimmer of hope for NZ First would be if all the non-National party supporters in Tauranga threw their electorate votes behind him. If he won Tauranga the party votes for NZ First would not be wasted and any list MPs he was able to drag through on his coat tails would be added to a Labour-led government. But don't hold your breath on this.

Progressive Party supporters

Their sole MP, Jim Anderton, is a reliable Labour ally. He won't win enough votes to bring in an extra MP, so his supporters should give their party vote to Labour to help them win an extra seat that may make the difference in Clark keeping her job.

Maori Party supporters

These are the crucial voters. If you are enrolled on the Maori electoral roll, it's a no-brainer. You give your electorate vote to the Maori Party candidate so it wins all seven seats. Ironically, Clark's only hope of being returned to power is if her Labour candidates are defeated by the Maori Party.

Even if Labour lost all their Maori seats, it has no effect on the total number of MPs that Labour gets. The total number of MPs a party gets is determined by the number of party votes they get - not the number of electorate seats they win.

If the Maori Party wins all the seven electorates it will still need 6 per cent of the party vote to get an eighth MP from its party list. That won't happen and in those circumstances their list votes are wasted.

Therefore it's better for the centre-left if the Maori Party gets a smaller party vote total provided it wins more electorate MPs than it would be entitled to from their party list vote. This would create a "parliamentary overhang".

Therefore, if the Maori Party won all seven seats but only won 2 per cent of the party vote, it would have five more MPs than its list allocation. This would result in 125 MPs in a new parliament, rather than the usual 120. Clark or Key would then need 63 MPs rather than 61 to have a majority.

This situation would advantage Labour rather than National because Clark has more coalition partner options than Key. However, if the Maori won all seven electorate seats but got 5 per cent of the list vote, it wouldn't add any extra MPs and so there would be no parliamentary overhang.

Here's a simpler explanation: If National got 48 per cent of the party vote it would get 58 MPs. Assuming its allies Act and United Future got four MPs between them, that would give the centre-right combo 62 MPs, making a majority in a 120-seat parliament.

But if there was an overhang parliament of 125, Key would be one seat short. That would mean if the Maori Party supported Labour, Clark would win a fourth term.

So, even though Labour's trailing in the polls and did not have a great campaign last week, there is still a possible path to victory if the non-National electors vote strategically.