Hunch. Christopher Luxon ruled out a deal with the Opportunity party in August, and early October polls give that party the deciding seats.
The National market resolves on official government announcements at beehive.govt.nz: YES if by the end of 3 December the National leader is named prime minister of the new government under signed deals or is sworn in, and NO if another party's leader is; if the government site cannot be read, Guardian and BBC reports of the swearing-in settle it. If no new government is named by 3 December, the market is void and does not count.
We looked for cases where New Zealand's governing parties faced voters under the system used since 1996, where seats follow each party's share of the vote. We found ten such elections, from 1996 to 2023. In six, a new cabinet was named or sworn in within 20 days of the vote. In the other four, talks took 32 to 65 days, and each time New Zealand First had the deciding seats. In most of the ten, the government side did not keep a majority on election night.