Even when only National voters were asked, 54 per cent said they should have been told before the election. Thirty-three per cent said no and 13 per cent didn't know. 3News political editor Patrick Gower said the poll was a "shock result that would shake the Beehive".
"It's a game-changer. It shows Peters in the lead with a genuine chance, and it shows voters are punishing National over the Mike Sabin issue," he said.
The byelection, expected to cost taxpayers up to $1 million, was forced by the resignation of National MP Mr Sabin last month.
If Mr Peters wins the byelection, the balance of Parliament will be altered.
National will no longer be able to rely on Act's single vote to get its way, and may struggle to pass contentious legislation such as its planned RMA reforms.
United Future leader Peter Dunne has already signalled he would expect a higher price for his support if Mr Peters wins.
Asked before the poll came out what he thought his chances were, Mr Peters said he was "very much the underdog" but he would give the byelection his best shot.
But by the time Mr Peters' Force for the North bus arrives in the Kaipara towns of Te Kopuru, Dargaville, Ruawai and Maungaturoto today, he will be the candidate the other parties need to beat.
Mr Peters used his stop in Kerikeri yesterday to hammer home his message that Northland had been long neglected by National, and the upcoming byelection was voters' best chance in decades to send the Government a message of their own.
He said National's claims of having created 7500 jobs in the North were "scatology" and money that used to be spent on Northland roads was now poured into a handful of Roads of National Significance, none of which would come further north than Wellsford.
If he got in he would push for improved transport infrastructure including a railway line to Marsden Port, giving the North a closer outlet for its products.
Poll shock
*Winston Peters (NZ First) 35 per cent
*Mark Osborne (National) 30 per cent
*Willow-Jean Prime (Labour) 16 per cent
*Don't know 11 per cent
*Won't vote 8 per cent
*3News Reid Research poll of 500 people, margin of error plus or minus 4.4 pc.