National also announced its candidate for the June 9 byelection.
Foodstuffs strategist Dan Bidois, 35, was chosen from a shortlist of five earlier today.
The byelection, with a price of around $1 million, was triggered by the resignation of local MP and former health minister Jonathan Coleman.
Coleman has held the seat since he first entered Parliament in 2005 but he is moving on, taking up the role of chief executive for Acurity Health Group at the end of April.
Northcote will be the first public test of new National leader Simon Bridges.
It is also the public's first chance to have a say on the way Prime Minister Jacinda Ardern and her Government are running the country.
If Labour manages to wrest the seat off National, it'll gain a seat in Parliament and National will lose one.
That won't change the Government's working majority much - 64 seats to 56 - as they will still have to rely on both NZ First and the Greens to pass legislation.