New Zealand First is fighting for survival with a quarter of the votes counted.
If Winston Peters was hoping that Ron Mark might help New Zealand First find a second electorate seat, with Mr Peters struggling in Tauranga, the strategy does not appear to be working.
Overall, with a quarter of the votes now counted National is maintaining its strong lead with 47.8% and Labour on 31.9%.
Ron Mark is running a distant third in Rimutaka.
With just 5.6 per cent of the vote counted, he is well behind Labour's Christopher Hipkins (1461 votes) and National's Richard Whiteside (1,392).
Ron Mark has 552 votes.
Winston Peters, meanwhile, is lagging almost 3500 votes behind National's challenger Simon Bridges.
In the party vote, NZ First is polling at 4.3 per cent - short of the 5 per cent threshold, which it has not crossed since counting began two hours ago.
New Zealand First are on their way out, a political expert says.
The party is polling below 4.5 per cent and Winston Peters and Ron Mark are both trailing by a long way in their respective seats.
University of Auckland political science lecturer Jennifer Lees-Marshment said: "I expect they'll go down further, it's so difficult to tell at this stage but I'd be surprised if they got over the five per cent."
She said the early results were coming from the smaller towns and favoured the right-wing parties. "I think Winston Peters is going to be on his way out after this election," Dr Lees-Marshment said.
She said the troubles that have plagued Mr Peters this year have put people off New Zealand First.
However, Political science lecturer Stephen Levine, from the Victoria University of Wellington, New Zealand First is doing better than the polls predicted.
"I'm not sure the polls were having New Zealand First over 4 per cent, so it keeps New Zealand First competitive but it's another victory for the pollsters in that Simon Bridges is so far ahead of Winston Peters and it was fantasy land for Ron Mark to win Rimutaka," Dr Levine said.
Earlier, with around 10 per cent of the vote counted, 11 National challengers were ahead of the incumbent MP or the Labour candidate where a Labour MP is retiring.
They include Stephen Franks in Wellington Central, where Labour MP Marian Hobbs has retired, National list MP Kate Wilkinson ahead of Labour cabinet Minister Clayton Cosgrove in Waimakariri and Todd McClay leading Labour cabinet minister Steve Chadwick in Rotorua.
Three key electorate battles are proving fascinating.
In Christchurch Central, Labour's Brendon Burns, who is seeking to replace Tim Barnett, is behind National's Nicky Wagner.
In Auckland Central, held by Labour, National's Nikki Kaye is leading Judith Tizard by 270 seats. Kaye is just 29 years old and one of National's young guns.
And in West Coast-Tasman - one of the key seats for Labour since its history is tied up among the unions of the mining industry - Labour incumbent Damien O'Connor is trailing Nationals' Chris Auchinvole by several hundred votes.
Meanwhile, the Maori Party appear to be making inroads in the Maori electorates, although Labour are holding off big challenges in Hauraki and Ikaroa-Rawhiti. The Maori Party are ahead in five of the seven seats.
Currently, the Minister of Maori Affairs Parekura Horomia is holding off a strong challenge from his Maori Party rival Derek Fox in Ikaroa-Rawhiti. With around 10 per cent of the vote counted, he is ahead by just 112 votes.
Nanaia Mahuta has a slim lead in Ikaroa-Rawhiti over Labour's Angeline Greensill.
But in all seven seats the margins are close at this stage.
National Party President Judy Kirk was one of a handful of supporters at the party's Sky City Convention Centre at the start of the evening. She says she is cautiously confident, but has warned against reading too much into the early results.
"It depends what booths come in first - we know from last time we had some of our strongest booths coming in first and you have to be careful not to get too carried away until you see the bigger picture," she said.
Labour's Phil Goff says it is too early to read anything into the results as rural seats always come through first and favour National.
Labour leader Helen Clark is bidding to win a record fourth term, while National's John Key is seeking to return his party to power.
Other crucial issues which will unfold durign the night are the fate of New Zealand First and the Greens as well as the other minor parties.
Turnout is tipped to be high thanks to good weather nationwide and strong advanced voting.