Key and Cunliffe to go head to head

Labour leader David Cunliffe and Prime Minister John Key will face off in first televised election debate tonight - but the psychological warfare started early.

Mr Cunliffe pulled out the underdog card, saying his rival's strong performances against former Labour leaders Helen Clark and Phil Goff had taught him to have some respect for his abilities.

"He's very polished and I'm the new kid on the block. So I recognise I've got a lot to learn.''

Mr Key moved to try to stifle any underdog status for Mr Cunliffe, saying he should not be underestimated: he had been in Parliament longer than Mr Key and was an experienced debater.

In an apparent attempt to psyche out Mr Cunliffe, Mr Key spent the morning meeting shoppers at Albany before making two health announcements, while Mr Cunliffe locked himself away all day to prepare for it.

Mr Key said that he hoped to get in some time shooting hoops with son Max this afternoon but would put in a bit of time for prep.

Mr Key denied he was playing mental games with his apparently relaxed attitude, and said he had campaigned on debate days even when he was Leader of the Opposition in 2008.

"It's different strokes for different folks. But I'm expecting a tough debate tonight. David Cunliffe has been in Parliament longer than me, he's been a minister, everybody knows he's a good debater. I haven't taken him lightly.''

Both also admitted they had done some practice runs with stand-ins for their rival - but neither would say who those stand-ins were.

The performance of moderator Mike Hosking is likely to get just as much scrutiny as the two leaders. Mr Cunliffe had initially objected to Hosking as the moderator because he had spoken favourably about Mr Key and National in the past.

Although rough politics has dominated the campaign, Mr Cunliffe said he intended to keep the debate clean, saying his primary aim was to show New Zealanders he was ready to be Prime Minister.

"I don't think Kiwis would appreciate some kind of headbutting contest between the two of us.''

Although WhaleOil blogger Cameron Slater's return to New Zealand and his police complaint risked raising Dirty Politics again, Mr Key said voters were more interested in the economy, health and law and order than Slater.

"I suspect the million or so viewers that watch that will be really interested in the things that drive this country and the changes we make. What a blogger does or doesn't do is not likely to be top of mind.''

He said the ability to set out a plan was what could change votes in such a debate, not just "a zinging one-liner'' despite flooring Mr Goff in 2011 with his 'show me the money' line.

"The 'show me the money' came out of the top of my head in a debate about Labour's inability to get the numbers to add up. Three years later and the numbers still don't add up so maybe I can just use the same one-liner.''

As for superstition, Mr Key is likely to wear his lucky cufflinks tonight. Mr Cunliffe said he did not have any similar superstitions, but would spend a quiet few minutes alone just before the debate. Asked if he would use that to pray, he said "maybe.''