The countdown is on to this election's first Leaders' Debate.

Labour's Chris Hipkins and National's Chris Luxon go head-to-head on TVNZ from 7pm.

Former National Prime Minister, Sir John Key, says Luxon's the under-dog - and may have the tougher job.

"There are actually a lot of people who want to vote for him and want to vote for National- so they will just be making sure he's the real deal. So there's a lot to play for Chris Luxon."

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