Polls describe sentiments poles apart

Jim Bolger famously said "bugger the polls" when he nearly lost the 1993 election after appearing set to win comfortably.

He would be excused a wry smile this week when TV1's Colmar Brunton put National ahead of Labour by 8 percentage points and TV3's TNS put Labour ahead of National by 7 points three days later.

The Herald DigiPoll survey's dead heat came in neatly between them - though perhaps showing a slight trend in Labour's favour.

Who is right? We can't tell. But comparing Colmar Brunton with the totality of all polls over the past three parliamentary terms shows it rates National more than 2 per cent higher than the average of all polls (and Labour about 0.3 per cent lower). TNS has under-rated National by 1.3 per cent and over-rated Labour by 1.2 per cent this parliamentary term compared with the average of all polls.

But even allowing for that leaves a big gap.

So are voters still big swingers or was one or both of those polls among the one-in-20 that statistically fall outside the margin of error - "wrong", as Labour strategist Pete Hodgson labelled Colmar? We don't know - though DigiPoll's figure has the most credible ring.

What we do know is that to the extent that polls are useful they are painting a tight race. The chart shows Helen Clark's governing combination in red and three possible options for National (of course, New Zealand First could go with Labour, which would weight the picture in Labour's favour)

Tomorrow there will be two more polls: BRC in tomorrow's Sunday Star-Times, taken slightly before the DigiPoll survey, and TV1's Colmar Brunton, taken during this week. We must wait till next week, however, for a measure of Don Brash's about-face on the Exclusive Brethren's un-Christian attacks on Labour and the Greens.

* 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 survey, Colmar Brunton (TV1), UMR (National Business Review), TNS (TV3) and BRC (Sunday Star-Times). All five are in the mix at all times, but the average at any one time is a different combination of the five polls. The latest average is: DigiPoll twice, polling midpoints August 28 and September 4, Colmar Brunton, midpoint August 30-31 and TNS, midpoint September 3-4.