KEY POINTS:
Polls at the weekend showed wide variations four weeks from the election, ranging from a very narrow to a very wide lead for National over Labour.
Taken over the whole of 2008 the rolling average of polls shows a near-flat trend for National (around 51 per cent) and a very slightly declining trend for Labour (around 35 per cent).
But, as the chart shows, the trend from Budget time in May is down for National, to a little below 50 per cent in late September-early October (the latest actual average is below-trend).
Projected forward to election day, the trend would be around 48 per cent, enough for National to govern with the support only of Act and United Future.
Labour's trend has been up since May to around 36 per cent, which projects forward to nearly 37 per cent on election day.
Just 1-2 per cent more would make it competitive, if it could recruit the Maori Party (or a resurrected New Zealand First) to add to the Greens and Jim Anderton.
Of the small parties, only Act has been trending up since the Budget. If the trend holds, Sir Roger Douglas will be back.
The Greens' latest average is a little under 8 per cent but the trajectory is down, pointing to just below 6 per cent on election day. New Zealand First will be hoping for a lift from the Serious Fraud Office part-clearance.
The Maori Party's and United Future's trends have been flat.
