Support for the National Party has dropped 2.5 points to 45 per cent, and the party would need the support of New Zealand First to govern. John Key has fallen a similar amount in the preferred Prime Minister stakes, down to 41.4 per cent.
The Labour Party also took a hit, falling 2.6 points to 26.4 per cent, although support for David Cunliffe as Prime Minister has risen slightly to 11 per cent.
The Green Party had 13.5 per cent support, while Internet Mana had 2.1 per cent support.
Conservative leader Colin Craig did not think the party was picking up votes in any fallout from Dirty Politics.
"I think the biggest impact is that our second brochure, which has gone out to every household in New Zealand, has arrived. It hit last weekend.
"Polls are a bit slow in picking things up, but it's probably true that leading the whole Lochinver Station deal is reflecting now as well."
Mr Craig gained prominence in the campaign when he lifted the lid on the possible sale of the station to Chinese buyer Shanghai Pengxin for $70 million.
The Conservatives' chances of entering Parliament were dealt a blow after Prime Minister John Key decided not to do a deal with the party, instead focusing on United Future and Act.
But Mr Craig said the 5 per cent mark now looked "extremely do-able".
3News-Reid Research poll
National 45% (down 2.5)
Labour 26.4% (down 2.6)
Greens 13.5% (up 0.5)
NZ First 6.3% (up 1.7)
Conservative 4.6% (up 2.1)
Internet Mana 2.1% (up .1)
Maori Party 0.7% (down .1)
United Future 0.4% (up .2)
Act 0.3% (NC)
1000 people polled, August 19-25. Margin of error: 3.1%
