National is now very likely to get an extra seat in the next Parliament. 

The traditionally safe National seat of Port Waikato will now be determined in a by-election on November 25, following the death of ACT's Port Waikato candidate Neil Christensen. 

In the meant time the 120th seat will be filled by a list candidate, likely to be from National's list. 

Otago University law expert Andrew Geddis told Mike Hosking that it's due to a rule that we inherited from the First Past the Post system. 

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