An Oamaru man was concerned to find he could vote multiple times in the text poll on Wednesday's TV One Leaders' Debate.
Malcolm McKenzie decided to experiment with the programme's text poll and sent in three votes within around 10 minutes of each other for his preferred candidate. He then sent in two votes from his wife's phone.
Mr McKenzie said each time he sent in a vote he received an automated text reply thanking him. There was no message saying he had already voted from that number and that his vote was invalid.
He said he was concerned people putting in multiple votes could have affected the outcome of the text poll, which had John Key ahead of Phil Goff with 63 per cent of the vote for preferred prime minister.
He said everyone he had talked to thought Mr Goff had done better than Mr Key in the debate and that the 63 per cent was too high.
Mr McKenzie thought National voters would be in a better position to afford the 75 cents each text cost.
A TVNZ spokesperson said it had no rules against multiple voting. Its polling company could see if there were a significant number of votes from one phone but that was not common. Different members of one family may well vote using the same phone, TVNZ said.
"Our polls are not scientific and we have never promoted them as such. They are simply an indication of which way the wind is blowing, and an opportunity for people who are really motivated to interact with our programmes. The cost of each call acts as a natural deterrent to any extremes.''
Bryce Edwards, from the University of Otago's politics department, warned that polls conducted by the media were inaccurate, as they made no attempt to recreate an accurate cross-section of society.
But perceptions created by polls and the media could have a large effect on people's voting behaviour.
"If a party is seen to be doing badly, people don't want to vote for them.''
Dr Edwards said the Labour Party was especially suffering from this phenomenon, and he thought voters might be disheartened by the party's poor portrayal.