Asked if it was possible that a loss by the All Blacks against France on Sunday, coupled with a gloomy economic outlook and the Rena shipping disaster, could create a malaise during the election campaign, Mr McCully said that would "read too much into unrelated events".
"But there's no doubt an overall feeling of goodwill is not unhelpful to any Government.
"So we obviously are going to wish to avoid anything that is going to make New Zealanders feel bad about themselves and their country."
In that respect, the biggest risks lay in the way in which New Zealand presented itself to the world, more than what happened on the rugby field.
Most of the six previous Rugby World Cup events were held too long before elections to draw any conclusions.
Two exceptions were the first one in New Zealand in 1987, when an election was held just two months later, and in 1999, when an election was held the same month.
In 1987, the incumbent Labour Government was returned for a second term with an increased majority. But a link has never been made between the events and neither Mr McCully nor Labour sports spokesman Trevor Mallard believes there was a link.
In 1999, nine years of rule by National ended the same month as New Zealand finished fourth. But National had been deeply unpopular before the Rugby World Cup after Jenny Shipley ousted Jim Bolger as Prime Minister and its coalition with New Zealand First disintegrated.
"The Shipley Government was doomed well before the election," said Mr Mallard "and well and truly before the Rugby World Cup result."
WORLD CUPS AND ELECTIONS
1987 - New Zealand winners and hosts
NZ hosted and won the World Cup on June 20, 1987. A general election was held in August, with Labour returned to a second term of Government with an increased majority and a 5 per cent swing.
1991 - Australia win, multiple hosts
The UK, Ireland and France hosted the event, with Australia beating England in the final, and NZ coming third. It was two years until an election in Australia, with the Labor Government returned with a 1.54 per cent swing in its favour. In NZ in the same year the National Government's majority was slashed after just one term with a 12.77 per cent swing.
1995 - South Africa winners and hosts
South Africa beat NZ in the final. The following year the first MMP election in NZ saw National form a minority coalition Government with its numbers cut in a 1.18 per cent swing against it.
1999 - Australia winners, many hosts
Australia beat France in the final. NZ began favourites but finished fourth. NZ had an election later that month and National's nine-year rule ended when Labour, with a 11.55 per cent swing, formed a Government.
2003 - England winners, Australia hosts
England beat Australia in the final, with NZ coming third. The next elections for the Australians came in 2004 when John Howard won his fourth term with a slight increase in support. The next NZ elections were in 2005; Labour held its support and formed a third- term Government.
2007 - S Africa winners, multiple hosts
South Africa beat England in the final. NZ was knocked out in a quarter-final against France in Cardiff. NZ's election in November the following year saw a 5.83 per cent swing to National, ending Labour's three terms in office.
