The Electoral Commission has confirmed a by-election will be held for Port Waikato, after ACT candidate Neil Christensen's death.
It is urging people in the area to still vote, as their party votes would still be counted - but the electorate will remain unrepresented until a by-election after the October 14 general election, on a date to be set by current Prime Minister Chris Hipkins.
The change appears likely to benefit the National Party, because an extra list seat will be added to make up for the lost electorate seat in the election.
The Port Waikato electorate seat will then be added to the Parliament after the by-election, meaning 121 seats overall - barring any additional overhang seats - and is likely to then be won by incumbent, National's Andrew Bayly.
At 15th on National's list, Bayly is all but guaranteed to make it back in on the list during the election, so the party would be able to bring in another MP from its list.
ACT leader David Seymour announced Christensen's death in a statement on Monday afternoon.
"I wish to pay tribute to Neil, who was an infectiously charismatic and fascinating man and was New Zealand's only registered specialist poultry veterinarian," Seymour said.
Chief electoral officer Karl Le Quesne said the commissions thoughts were with Christensen's family, and extended his condolences.
Le Quesne is expected to speak to Checkpoint about 6pm.
Look back over Monday's updates with RNZ's election blog:
