Crowd continues to trickle in to Act party leader David Seymour's election party

Act Party faithful have started converging besides the Auckland Harbour Bridge on a still spring evening, confident of a win in the Epsom electorate for party leader David Seymour.

The incumbent Epsom MP goes into election night 2017 with the backing of the National Party and polls indicating an easy win for Act in New Zealand's wealthiest electorate.

While the party itself has been polling well below 1 per cent, it is expected Epsom voters will give Seymour the orange tick, a result that would shore-up a National-led Government.

National's Epsom candidate, Paul Goldsmith, has campaigned for party votes but endorsed Seymour to retain the seat, just as he did in the 2014 election.

Anything but an Act victory in Epsom would be a complete unthinkable for the right-wing libertarian party.

Act election night HQ is the Royal New Zealand Yacht Squadron building on Westhaven Marina, overlooking the shimmering Waitemata Harbour.

Masses of yellow balloons and enlarged pictures of Seymour's boyish face adorn the plush room.

Upwards of 100 people, many of them media or party members, were present when the televisions were turned on at 7pm.

But the crowd continued to trickle in and order tall glasses of vino from the well-dressed bar staff. Seymour himself is rumoured to make an appearance about 8pm.

Act's Epsom Electorate campaign chairman Malcolm Pollock said tonight marked the end of months of hard work, which included dropping over 125,000 pieces of mail in Epsom.

"I'm confident we're going to win Epsom, I'm not complacent," he said.

"So I'm confident that David will get back in, I'm less confident that we'll get the additional MPs that I think Act deserves and I think that's primarily because we just haven't had the ability to get the airtime that the other leading parties have had."

Act's 19-year-old Ohariu candidate, Andie Moore, was more optimistic, predicting gaining three MPs with something like 1.8 per cent of the party vote.

"Overall I think Act's had a very positive campaign - we've had lots of positive feedback. Housing's been a big issue; everyone's reacted to that well. Youth crime, education - everyone has seen Act has very solid policies."

He said Act usually polled lower than the votes it actually garnered at the ballot box.