See-saw battle of the parties not seen since 1981

There hasn't been a contest like this between the two big parties, with the lead swinging back and forth, since 1981.

Then, Labour won a sliver more of the popular vote than National but narrowly lost on seats. In 1984 and 1987, National was not in the hunt. They swapped positions in 1990, Labour weak and National strong. In 1993 and 1996, Labour and National were both weak, and in 1999 and 2002, National was a distant second again.

Don Brash and the Treaty of Waitangi have changed all that.

The polls have been a see-saw. Going into 2004, Labour was averaging 46 per cent and National 26 per cent. By March, after Brash's Orewa I speech, the ratings had whiplashed: National 45 per cent, Labour 38 per cent. By year-end, however, Labour was back on top: 45 per cent to National's 34 per cent, the starting point for today's chart.

Through the autumn, as the general mood and consumer confidence slid, so did Labour.

When the Cabinet lost its sure-footedness in April-May and the Budget went awry, National leaped back in front, 40 per cent to 37 per cent - only to reverse out just as quickly in July-August under Labour's anti-nuclear and student loan onslaughts.

Take out the June-July results and National is on the slow, upward track it was on pre-autumn, heading towards maybe 38 per cent to 39 per cent, with Labour still well-placed.

But that reckons without Monday's tax cuts. Might they - or another Treaty uproar - shoot National back in front? With four weeks to go, the result is still open.

* Each week the Herald examines an aspect of the poll-of-polls. Each point on the chart represents the average of the four most recently published of the Herald DigiPoll, Colmar Brunton (TV1), UMR (National Business Review), TNS (TV3) and BRC (Sunday Star-Times). All five are in the mix at all times, but each point represents a different combination of four of the five polls.