As the results start rolling in, some electorates are much more important than others because they will decide if some parties remain in Parliament.

These are the battleground seats to keep an eye on throughout tonight:

Epsom

Act leader David Seymour must win Epsom's seat to remain in Parliament. Photo / Richard Robinson
Act leader David Seymour must win Epsom's seat to remain in Parliament. Photo / Richard Robinson

Epsom is the must-win seat for Act leader David Seymour to remain in Parliament.

Act has no chance of reaching the MMP threshold of 5 per cent of the party vote to get members of its list into the House - it was yesterday at 0.41 per cent in the Herald prediction model, based on national opinion polls and past election results.

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So Act has to rely on the other route to Parliament: winning an electorate.

To help Act with this, National has stood aside in Epsom for the fourth consecutive election. National's candidate in the central Auckland seat, Paul Goldsmith, said during the campaign he was focused on the party vote rather than on winning the seat.

Act said in June a poll in the seat had Seymour leading on 46 per cent of decided voters the electorate vote, followed by Goldsmith on 30 per cent.

At the 2014 election, Seymour won with 43 per cent of the electorate vote and majority of 4250, while National took 63 per cent of the party vote.

Waiariki

Maori Party co-leader Te Ururoa Flavell is going up against Labour candidate Tamati Coffey. Photo / Stephen Parker
Maori Party co-leader Te Ururoa Flavell is going up against Labour candidate Tamati Coffey. Photo / Stephen Parker

Waiariki is another lifeline seat - this one for the Maori Party, which was yesterday sitting at 0.68 per cent of the national party vote in the Herald prediction model.

Maori Party co-leader Te Ururoa Flavell looks likely to retain Waiariki with a good majority - a Maori TV poll 13 days ago put him on 60 per cent.

His sole opponent, Labour's Tamati Coffey, a former TV weatherman, was on 40 per cent.

But when broken down by age, the picture was variable: Coffey was ahead among voters under 35; Flavell was in the lead with those aged 35 or older.

In 2014, Flavell won against three opponents, taking 45 per cent of the electorate vote and a majority of 3889.

Nelson

National's Nick Smith has held Nelson since 1996, but the Green Party has been talking up their internal polling. Photo / Supplied
National's Nick Smith has held Nelson since 1996, but the Green Party has been talking up their internal polling. Photo / Supplied

After the Green Party dipped to around the 5 per cent threshold in national polling - it's back up to 6.46 per cent in the Herald prediction model - its Nelson candidate Matt Lawrey began talking up internal polling showing a three-way race for the electorate vote.

The Green Party hasn't won an electorate since Jeanette Fitzsimons held Coromandel from 1999 to 2002.

National's Nick Smith has held Nelson since 1996 and in 2014 took a commanding majority of 7605, winning 53 per cent of the vote.

He attacked the method used in the Green's Nelson poll, which put him only a few percentage points ahead of Lawrey and the Labour candidate Rachel Boyack.

Te Tai Tokerau

Hone Harawira lost the Te Tai Tokerau seat in 2014. Can he win it back? Photo / Mike Scott
Hone Harawira lost the Te Tai Tokerau seat in 2014. Can he win it back? Photo / Mike Scott

Mana Movement leader Hone Harawira is trying to win back his old seat of Te Tai Tokerau in Northland from Labour's Kelvin Davis.

The field was narrowed for Harawira in February when, in a Maori seats deal, Mana and the Maori Party agreed not to stand candidates against each other.

Davis tipped Harawira out of the Te Tai Tokerau seat in 2014, with a slim majority of 743 over Harawira and 44 per cent of the electorate vote in a field that also included the Maori Party and an independent candidate.

A Maori TV poll published this month put Davis well in front, on 64 per cent, to Harawira's 30 per cent. Harawira attacked the polling methods, and highlighted a poll by National-linked Curia which had found a 10-point gap between the two candidates.

Mana is at 0.08 per cent of the party vote in the Herald prediction model.

Northland

Winston Peters has said he is confident he can win Northland. Photo / Nick Reed
Winston Peters has said he is confident he can win Northland. Photo / Nick Reed

New Zealand First's 7.58 per cent in the Herald's prediction model would be enough for the party to avoid another spell as political outsiders, but leader Winston Peters is campaigning hard to retain the security of his Northland seat regardless.

Peters has said he is confident he can retain Northland, the traditionally National seat he snatched in a by-election following the resignation of Mike Sabin in 2015.

Peters took the seat with 54 per cent of the vote and a majority of 4441 over National's Mark Osborne. Sabin had retained the seat with 52 per cent of the vote in 2014.

Peters faces two strong candidates in National's Matt King - former police officer, former Honda motorbike salesman, business owner and farmer - and Labour's Willow-Jean Prime, a Far North District councilor who took 26 per cent of the Northland electorate vote in 2014.