I'm suspicious that the polls favor either party universally. I know in the Indiana 7th Congressional District (Indianapolis, basically) the polls have shown a close race the last 3 cycles. But the actual election occurs and the long-time incumbent Democrat wins by 8% or more. And yet I kept hearing this time that the polls were different and more accurate. Whatever...

 

The last elections here underlined very heavily just how useless polls are, although the last election here was kind of unusual.

The polls were all variously saying that either Labour or National were ahead by 6-7%, depending on the poll. They also showed all of the larger minor parties as having ~8-10 seats each.

Election comes around - Labour narrowly wins and the minor parties all end up with only a 3-6 seats each, with the Maori party getting 4 seats instead of the projected 0.

Turns out that rural areas heavily favoured National and urban areas heavily favoured Labour, so any poll that was conducted primarily in those types of areas would have results that leant in their favour.

So much for polls, all of which claimed 3-5% margin of error and were well outside that range on election night.

A further complicating factor in that particular election is that you couldn't look at the poll results from the previous election and use them as a guide - National had its lowest turnout since the parties inception back in the 1800's, getting only 22% of the vote. Some political commentators were saying that at those levels, it could basically be considered to be a 'large minor party'. The minor parties all picked up the slack, with the Greens getting 13 seats (they now have 6), NZ First getting something like 8 (now has 5 or so) and the christian coalition getting 9 or so, now on 6.