Next National Party leader will lose to Jacinda Ardern - Bryce Edwards

National is picking its new leader on Tuesday, but there's doubt any of the candidates will be the next Prime Minister.

The 56-member caucus meets at 10:30am and five candidates get their last chance to pitch for the job ahead of a secret ballot.

Amy Adams and Simon Bridges are believed to have the most support in caucus, with Judith Collins, Steven Joyce and Mark Mitchell also in the running.

However, political commentator Bryce Edwards is sceptical about their chances at the 2020 election.

"I'm not sure we've seen anything from this leadership contest that really should give the National Party that much confidence that they're going to have a leader that really does have what it takes to compete with Jacinda Ardern," he says.

No one is likely to get the 29 votes needed to win on the first ballot. The lowest-polling contender will drop out and voting goes on until one of them has the support of a majority of caucus members.

Ms Collins is unlikely to do well in the vote but has been the most proactive in drumming up public support during the campaign.

Mr Edwards says Judith Collins has been the best performer and she's proven her skills.

"She's so bold, she's entertaining," he says.

"You don't get the traditional vagueness and evasions that you often get these days from politicians."

NZN / Newshub.