The Oxford Dictionary definition of a "honeymoon" is, as well as the post-wedding variety, "an initial period of enthusiasm or goodwill".
There is no time limit on a honeymoon, but they usually do not last for more than four years and almost certainly do not last that long in politics.
However, in the fifth year of his premiership, Mr Key's personal popularity has stayed above 60 per cent in the Herald-DigiPoll since he became Prime Minister in 2008, apparently only slightly bruised by the winds that have battered his government.
His predecessor, Helen Clark, never made it above 60 in the survey. Her high point was 59 per cent one month before the 2005 election. Mr Key's peak was 72 per cent in February 2010 - although he shot from 46 per cent to 70 per cent almost overnight after being elected Prime Minister.
In comparison, Helen Clark was a slow starter whose honeymoon was delayed. She hit 56 per cent four months after becoming Prime Minister in 1999 in a minority coalition with the Alliance. They lingered in the 30s and low 40s until the 2002 election.