Labour will have very mixed feelings about being forced by one of its MPs to fight a byelection in Mana, even though it is one of the party's safest seats in the Wellington region.

The byelection sparked by Winnie Laban's departure to a job at Victoria University is a nuisance for Labour and an opportunity.

It is a nuisance because Labour is on a hiding to nothing. Mana is behind only Annette King's Rongotai in the majorities in the five seats Labour holds in the capital.

Laban's majority is a healthy 6155 votes. Because of her her popularity, the more pertinent guide may be the electorate's party vote, which Labour won in 2008 by a much narrower margin of around 2500.

If the unthinkable happened and Labour lost the byelection, Phil Goff's leadership would not just be thrown into further question. He would be fighting for his political life.

If that was not enough for Goff to worry about, there is the memory of National's awful campaign in last year's byelection in Helen Clark's old seat of Mt Albert. That was a textbook example of how things can go dreadfully wrong in a byelection.

But like it or not, Labour is stuck with a byelection after Laban's decision to take the university job, made without first telling her party's leadership.

That speaks volumes about how some Labour MPs view the party's prospects at next year's election.

Those MPs not heading for the exit have to view the byelection not as a nuisance, but as a much-needed opportunity for the party to lift its profile and road-test some new ideas.

As it did in Mt Albert, Labour will mobilise its members and supporters throughout Wellington and the Hutt Valley to canvass door-to-door. The party will heavily plug local issues, as it did in Mt Albert.

Labour will be helped by two factors. Mana is a rather atypical electorate. The southern boundary takes in some of the poorest suburbs in the country - Cannons Creek and Porirua East. At the northern end is Raumati Beach, a retirement mecca for many top public servants.

The difference in socio-economic status is illustrated by the high number of primary schools in the top and bottom deciles. The lack of many in the middle points to the relative absence of middle-ground voters who could swing the seat to National.

This analysis is supported by a comparison between the results of the 2005 and 2008 elections. When Labour was ousted in 2008, its party vote fell by only 800 in Mana. Laban did better in the electorate vote that year than she did three years earlier.

Those factors suggest Labour can hold Mana - as long as it does three things.

First, it must select the right candidate. In Labour's case, the demographics dictate that person be of Pacific Island lineage.

Second, it must move heaven and earth to get its voters to the ballot box on polling day.

And third, byelection day must wait until Mana voters are feeling stung by the October 1 hike in GST. The least Laban could do is delay her resignation from Parliament accordingly.