United Future leader Peter Dunne faces a tough battle for his Ohariu seat after Labour kicked off its campaign and National vowed it would not stand aside to give him a free ride.
List MP Charles Chauvel will begin door knocking and leaflet drops within weeks after he was the only nomination as Labour's candidate.
The seat is the eighth most marginal in the country. It was held by Mr Dunne by just 1006 votes at the last election – well down on his 7702 majority in 2005 and the 12,000-plus margin he racked up in 2002.
It is one of five seats Labour will go all out to win, and in which candidates will be confirmed by March.
Mr Chauvel's candidacy must still be approved by the local branch, but is expected to be rubberstamped as he was Labour's candidate in 2005 and 2008, coming second both times.
He believed the seat was ripe for the picking. "There's the issue of people tiring of the idea of a sitting member who will just align himself with whoever seems to be likely to be the government, but I think also there's a fatigue factor ..."
Labour's targeting of the seat raises questions of whether National will consider standing aside to ensure Mr Dunne returns to provide an extra option if it cannot govern alone after 2011.
It did not stand in Ohariu for that reason in 1996 and Prime Minister John Key effectively signalled to National supporters to back Mr Dunne in 2008 after he agreed to be part of a National-led government.
But National list MP Katrina Shanks, who has also contested the seat at the past two elections, said she "absolutely" intended standing again. "`I'm definitely putting my name forward. It's going to be anybody's at the next election."
Mr Dunne won 12,303 votes in 2008, compared to 11,297 for Mr Chauvel and 10,009 for Ms Shanks.
National's lower North Island regional chairman, Malcolm Plimmer, also insisted National would stand in the seat.
Mr Dunne declined to comment on Mr Chauvel's candidacy.
Losing the seat would spell an end to his political career unless UnitedFuture gets above the 5 per cent threshold for list seats, something it has achieved only once.
The other seats Labour is aiming for are all former strongholds lost at the last election.
They are Auckland Central, Maungakiekie and West Coast-Tasman, where there was also only one nomination, and Waitakere, where four candidates will go forward for selection on March 20.
They are list MPs Phil Twyford, Carmel Sepuloni, Ann Pala and Hamish McCracken.
List MP Jacinda Ardern was the only nomination for Auckland Central, where she will take on Nikki Kaye who won the seat for National for the first time in 2008.
List MPs Damien O'Connor and Carol Beaumont were the nominations for West Coast-Tasman and Maungakiekie respectively.
- © Fairfax NZ News
Should Judith Collins resign?