Bill English will have to defy modern New Zealand political history if he's to keep his job as Prime Minister after September 23.
Not since Peter Fraser in 1943 has an incumbent Prime Minister who succeeded into the job during a parliamentary term won the next election.
Fraser, who became Labour leader and PM after the death of Michael Joseph Savage in the early months of World War Two, led his party back to the government benches in both 1943 and 1946.
The sequence set in. The first National Party Prime Minister Sid Holland relinquished the job to Keith Holyoake in 1957 because of ill health, but Labour and Walter Nash narrowly won the election that year.
National, still led by Holyoake, were back in charge in 1960 and then won the next three elections. But in 1972 Holyoake stood aside for his deputy Jack Marshall.
Labour under Norman Kirk stormed to victory 55 seats to 32 with 48.4 per cent of the popular vote.
However, Big Norm, never the healthiest of individuals, died less than two years later and Bill Rowling became Prime Minister.
A resurgent National under Rob Muldoon swung the 1972 vote on its head and exactly reversed the state of the parties in 1975. Rowling had lasted barely 15 months as PM.
The next mid-term change of Prime Minister came in 1989.
David Lange, having led the Fourth Labour Government through the 1984 and 1987 elections, had an ideological fallout with his Finance Minister Roger Douglas and quit the job in August 1989.
Labour's then deputy Geoffrey Palmer succeeded into the job but only 13 months later, when it was obvious Labour would not win the 1990 election, he was replaced by Mike Moore only six weeks out from polling day.
It made no difference. National, under Jim Bolger, won in a landslide 67 seats to 29 (with one to Jim Anderton of New Labour).
Bolger kept his job as PM through the 1993 and 1996 elections. But the landscape had changed. We voted for MMP in 1993 and the so called Great Helmsman only kept his job in 1996 after intense coalition negotiations with Winston Peters and New Zealand First.
But only a year later, the King Country farmer had lost the confidence of his party and the caucus installed Jenny Shipley as the country's first female Prime Minister.
She had two years and two days in the role, including a spectacular falling out with Peters, but was steamrolled by Helen Clark and Labour in December 1999.
It was nearly 16 years before there was another mid-term change in the Prime Ministership when John Key unexpectedly flagged it away.
So can Bill English do what Keith Holyoake, Jack Marshall, Geoffrey Palmer, Mike Moore and Jenny Shipley couldn't?
The polls tell us he has a reasonable chance, but he can't do it alone.
If those same polls are to be believed, then the numbers say English will only stay as PM if Winston Peters lets him.
But what price would Winston wish to extract to allow National to stay as the main governing party?
What about this scenario for 2017 - 2020?
"Mr English - you can stay as Prime Minister for now but I want a time in the big job before I finish in politics."
After being a National-led Coalition Treasurer and a Labour-led Coalition Minister of Foreign Affairs, is a 72-year-old Winston Peters going to settle for anything less than some time on the Beehive Ninth Floor?
Bill English might just to have to acquiesce otherwise he'll join the heap of post World War Two Prime Ministers who could not win an election.