Despite the polls, an English win at next year's election would be an historic achievement. Which makes the choice of when to go to the country, so very important

Even with a 20 point poll lead over the main Opposition party, history is against Prime Minister designate Bill English. While he will take over the Prime Ministership with plenty of hoop-la on Monday, he will be trying to defeat history as well as Andrew Little (and Winston Peters?) to take the top job again after next year's election.

In New Zealand, prime ministers who are anointed rather than elected rarely survive the next election. No substitute PM has won the job since Peter Fraser in 1943.

All have fallen at - or even before - the first hurdle.

Shipley lost two years after her coup to take over from Jim Bolger. Both Palmer and Moore fell when they took over at the end of the Lange years. Go back further and there are Hugh Watt and Bill Rowling in the 1970s, who couldn't win after Norm Kirk's death.

Given the frequent comparisons of John Key with Keith Holyoake, perhaps the best reference point for English is Jack Marshall, who got 10 months in the top job after Holyoake stepped down. While not finance minister, he was a long-serving, hard-working rock of his party, but one who was uninspiring and paled in comparison to his hugely popular predecessor. 

But of course events only ever mimic the past; history never repeats exactly. On each of those occasions, the leader who took over was facing either an economy in the doldrums or a party in crisis. English has neither. He is in the rare position of being a substitute PM with a tail wind.

Still, fourth terms are hard. There's a reason politicians talk about 'the nine year rule' in this country and it's because voters have a habit of tossing governments out due to dysfunction, third-term-itis or a sense they are stale and have run out of ideas. Key's popularity was such that he was odds on to buck that trend, but his resignation really has thrown his party to the electoral wolves. Now, English has to decide how he plays the cards he's been dealt.

Perhaps the biggest strategic decision is when to hold next year's election. There are strong arguments both ways.

The argument in favour of sticking to a September – perhaps even November – election is largely the argument against going early. The received wisdom is that voters don't like early elections and punish governments who push them to the polls too early. But the evidence of the past century doesn't support that.

We've had three early or snap elections in New Zealand and the incumbent has won two. In 1951, National used the waterfront strike to justify going to the polls, while in 2002 Helen Clark used the collapse of the Alliance as an excuse for a July election. Both won in a landslide. Only Rob Muldoon's famous drunken snap election in 1984 led to a loss, and that government was going to be toast whenever the election was held.

Shipley went close to calling an early election in 1997, when Winston Peters walked out of our first MMP coalition, but chose to tough out the term instead with a rag-bag group of rebel MPs. It was arguably a missed opportunity, and an especially surprising one for such a bold politician.

English, however, is inherently conservative. And he's likely to be especially so, when considering an early election in the middle of winter. That's exactly the scenario that played out in that 2002 landslide when Clark was PM; and it was English who suffered the defeat, winning a humiliating 20.9 percent of the vote. Does he really want to risk another winter loss?

He also lacks a proper reason to go early. A by-election or two is part of normal parliamentary business. In the century since the 1915 election New Zealand has held, by my count, 103 by-elections. At least one a year. To have one – or even to if Maurice Williamson is leveraged in as an excuse, two – is hardly destabilising for the government. The public – even the Governor-General – might look sideways at such a justification.

It's worth noting, when Holyoake stood down, Marshall went full term, trying to rejuvenate the party in the meantime.

But there are also good arguments for English to go early. On a matter of principle, it's arguable that he should seek his own mandate to run the country. Of course we are a parliamentary democracy and he is no president; as leader of the National Party, elected by the caucus as per the party's constitution, he has every right to lead the country given National's 2014 election win. But it's hard to argue with the conclusion that that wasn't largely John Key's win. The public backed him, but do they back English?

Of course there are political reasons as well. National has a 20 point lead in the polls over Labour; even as coalition partners, the Opposition parties do not look able to change the government at this moment. English may want to exploit whatever tail wind is left from the Key years (it still feels odd writing that!) while Andrew Little's popularity still pales in comparison.

Why give Little the chance to reframe himself as an alternative to English? Why not make hay while people still have him in their mind as an alternative to Key? Why let the image of Boring Bill or Bitter Bill take hold in the public imagination? Why not make the most of the good books English can say he, himself, has delivered? Why not make the most of any honeymoon the man from Dipton may enjoy? Because as a same-old, same-old politician with 27 years in parliament behind him and no real work experience outside the beltway (bar a short time on the farm), he's not likely to enjoy much.

Remember the fuss around Phil Goff being a 30 year veteran when he took over and the assumption that he was in no position to rejuvenate the party or be the face of change? He may think it's better to attempt a quick-ish win before voters wake up to the implications of no John Key.

And don't forget the internal issues within his own party. I wrote earlier this week that a pivotal part of Key's success was his ability to rein in the factions inside National. But now, even as candidates have stood aside for English, there are several senior people within the party who have a very good reason to wish that English loses next year, retires and opens the door for a proper leadership contest and new direction in opposition.

Whatever he chooses, English won't have it easy, with the weight of history pushing against him. But at least now, at long last, it's his choice to make.