2023 Port Waikato by-election

The 2023 Port Waikato by-election was held on 25 November 2023. The by-election was triggered by the death of Neil Christensen, who was a candidate for the ACT Party. Christensen's death occurred after the close of candidate nominations for the 2023 New Zealand general election, but before polling day. The by-election was won by National incumbent Andrew Bayly, who has held the Port Waikato seat and its predecessor Hunua since 2014.

2023 general election
Advance voting for the 2023 general election started on 2 October 2023. Christensen's death was announced on 9 October 2023, one week into the advanced voting period. Because New Zealand uses a mixed-member proportional voting system, Port Waikato constituents continued to cast a party vote vote in the general election, but the electorate vote was suspended and any electorate votes already cast were nullified. It was the first time since the 1957 election that an electorate vote had been delayed due to the death of a candidate.

One of the effects of the by-election will be that the winner will add another seat to Parliament beyond those elected at the general election. At the general election, the seat that would have been filled by the Port Waikato winner was instead filled by a list MP. The winner of the by-election will also enter parliament without ejecting any existing MP.

Electorate
The Port Waikato electorate was first established in 1996, ahead of the first MMP election. The electorate was abolished in 2008 and reinstated for the 2020 election. It stretches from the Manukau Heads at the southern entrance to the Manukau Harbour, south past the eponymous settlement of Port Waikato, to Matira and Pepepe, and inland to Mangatāwhiri and the Maramarua Forest. Pukekohe is the largest population centre in the electorate. Other significant towns include Pōkeno, Te Kauwhata, Tuakau and Waiuku. The electorate includes the New Zealand Steel mill at Glenbrook, and the lower reaches of the Waikato River.

Between the 2013 and 2018 censuses, the Port Waikato electorate experienced annual average population growth of 3.3%, considerably higher than the annual average rate for New Zealand as a whole (2.1%). The electorate is predominantly European (78.2%) and Maori (19.0%), with the shares of those identifying as Asian (8.8%), and Pacific Peoples (6.1%), somewhat lower than the average for New Zealand as a whole. Over a quarter (26.3%) of families had a combined income between $100,000 and $150,000 per year – the second-largest among general electorates.

Election schedule
Key dates relating to the by-election are as follows:

Candidates
All candidates had nominated to contest Port Waikato at the 2023 general election were re-nominated, unless they withdrew. On 20 October, the Labour Party announced that its candidate, Gwendoline Keel, would not contest the by-election, because the party viewed it as "unwinnable" and sought to focus on building a strong opposition against the newly elected government. Green Party candidate Karla Buchanan also withdrew her nomination, while ACT did not nominate a replacement candidate.

Andrew Bayly has held the seat since 2014. About a week before polling day, 1 News described Andrew Bayly as "a clear favourite", but that he was "facing a strong challenge from NZ First's Casey Costello".

Campaign
The Democracy NZ candidate, Scotty Bright, stopped campaigning and endorsed the New Zealand First candidate, Casey Costello, saying "It's about Port Waikato being represented by the best party, and we think NZ First has the best ability to do that."

Results
An estimated 18,759 votes were cast in the by-election, with an estimated turnout of 35.8% of the electorate. This compares to a turnout of 78.2% for the 2023 general election.

Final results show Andrew Bayly of the National party winning with a 11,432 vote margin over his nearest rival, Casey Costello of New Zealand First.

As Bayly had already been elected as a list MP in the 2023 general election, his win meant that National elected an additional MP from its list, Nancy Lu, who became the 123rd member of parliament.