National Leader John Key was the winner in TVNZ's leaders' debate, a Vote Compass survey says.
In the survey of almost 2,500 people, 58% believed Mr Key won the debate.
Thirty two per cent said Labour leader David Cunliffe was the winner, and 10 per cent didn't know.
People watching debates tend to be skewed towards the conservative end of the political spectrum, according to researchers from Vote Compass.
Among respondents identified as National supporters, 93% believed Mr Key had won, and 86% of Labour supporters said Mr Cunliffe won.
Green Party (55%) and New Zealand First (48%) supporters were also more likely to name Mr Cunliffe as the winner.
Though Vote Compass is not a poll, respondent data is weighted using the latest census data to approximate a representative sample of the New Zealand population.
The debate also got people talking on Facebook, with data revealing Mr Cunliffe was the most mentioned in posts during the head to head.
The most talked about issues on the social media site were taxes, the economy and wages and people aged between 25-34 talked about the debate more than any other age group.
ONE News Political Editor Corin Dann says he would give Mr Cunliffe a points victory in the debate over Mr Key.
"He surprised, he came out strong, he clearly had a strategy to come out and try and rattle the Prime Minister - he interrupted him quite a lot. Some people may have found that irritating and it may have detracted a little bit for him, but on the other hand he did get to land some blows and put the Prime Minister on the back foot.
"John Key looked a little flat-footed and a little quiet by his standards and David Cunliffe came across as the aggressor."
Television New Zealand will host a minor leader's debate next Friday and another head-to-head between Mr Cunliffe and Mr Key on September 17.
The findings are based on 2,464 respondents on August 28 who answered that they had watched the debate. Though Vote Compass is not a poll, respondent data are weighted using the latest census data to approximate a representative sample of the New Zealand population.