The National nomination for Botany looks to be down to a two-horse race between former broadcaster Maggie Barry and young Auckland councillor Jami-Lee Ross.

However, some National insiders say former Auckland City councillor Aaron Bhatnagar cannot be discounted in the selection race for the March 5 byelection - sparked by the resignation of former minister Pansy Wong.

National and Labour hold their final candidate selection meetings tomorrow for the byelection, which Labour president Andrew Little has said his party does not expect to win.

National's 13 contenders have been whittled down to Ms Barry, Mr Ross, Mr Bhatnagar, Darron Gedge and Edward Saafi.

Right-leaning political commentator Matthew Hooton this week said he believedit was a two-horse race between Ms Barry, 51, and Mr Ross, 25.

Hooton said on Radio NZ that Mr Ross had the advantage of being young and could bring voters to National who may not have voted for them before.

Gardening guru Ms Barry, who had conservation credentials and had appeared in advertisements for hearing aids, could be competition for New Zealand First leader Winston Peters in attracting older voters.

"If she does win that Botany election ... she will be able to hit that Grey Power circuit, the sort of areas where National is sometimes weak," said Hooton.

A National Party insider, who did not wish to be named, said Ms Barry's appeal would be "gold" to the party. However, he believed her lack of party experience could polarise delegates.

Delegates would rank Ms Barry first or quite low down - depending on whether they saw her as a great opportunity or too new to politics.

Whatever the outcome of this byelection, Ms Barry, Mr Ross and Mr Bhatnagar could all end up Parliament by 2014.

If Ms Barry does not win the selection, she could well get a high position on the list. Mr Ross is seen as a likely successor to Maurice Williamson in Pakuranga, probably in 2014, and Mr Bhatnagar is seen as a likely successor to Allan Peachey in Tamaki.

Labour's three hopefuls for selection are former Botany Community Board member Roy Bootle, Howick Local Board elected member David Collings and former Labour candidate for Pakuranga Michael Wood.

* Sixty delegates vote for candidate from a shortlist.

* Winning candidate must have majority support (31 votes). Weakest candidate drops out and ballots continue until there is a majority winner.

* Delegates are drawn from party members within the electorate, or from elsewhere in the region if there are not enough.

* Selections are made by a six person panel which comprises of three national council appointees, two electorate committee representatives and another local representative appointed in a vote from the floor of the selection meeting.

* The outcome of another ballot by local members at the meeting effectively serves as a seventh vote in the panel's selection process.