Waka jumping
Waka jumping is when a New Zealand member of Parliament (MP) either switches political party between elections (taking their parliamentary seat with them and potentially upsetting electoral proportionality in the New Zealand Parliament) or when a list MP's party membership ceases. The action is also called party hopping.
"Waka jumping" is a colloquial term that comes from traditional Māori waka (canoes). Hence, "waka jumping" is analogous to the seafaring term "jump ship", i.e., to leave a ship's crew abruptly and against the terms of a contract (or naval enlistment).
In 2001, legislation was enacted that required MPs to leave Parliament if they left their party; this law expired after the 2005 election. In 2018 a similar law was passed, which requires a defecting MP to give up their seat at the request of the leader of their former party. Electorate MPs may re-contest their seat in a by-election, whereas list MPs are replaced by the next available person on the party list.
A 2013 Fairfax-Ipsos poll found that 76% of those surveyed oppose MPs staying in Parliament if they leave their party.