One significant issue that divided National and Labour in the 1966 elections was the question of New Zealand's participation in the Vietnam War.

Under National, New Zealand contributed a small number of troops, which Holyoake strongly defended during the election campaign.

It had previously held office by a ten-seat margin — the drop was a result of losing the Hobson seat to Social Credit's Vernon Cracknell.

National won a total of forty-four seats, while the Labour Party remained static on thirty-five.

The table below shows the results of the 1966 general election: Key National Labour Social Credit