He emphasised at his post-Cabinet press conference on Monday that he would not be overexerting himself campaigning for the seat in the June 13 by-election and that National had never held the seat.
There were good reasons for Mr Key to play down the by-election.
First is the historic improbability that National can win it.
Not only has it never held the seat since the electorate was formed in 1946 but in the 40 by-elections in New Zealand since then, the party of government has never taken a seat from an opposition party.
By the end of the week, however, the news that Greens co-leader Russel Norman will contest the seat should have been enough for Mr Key to show a little enthusiasm for the fight.
Perhaps not a Clarkesque "Bring It On!" but the prospect of Dr Norman splitting the left vote will have given Mr Key a spring in his step.
It has certainly added some spice to the fight.
Labour was ahead of National on the party vote in Mt Albert last year by only 2426 votes, and the Greens got 3846.
The decision to stand Dr Norman will give the party profile but more importantly, it will give Dr Norman himself profile.
With senior co-leader Jeanette Fitzsimons stepping down in June and leaving politics at the 2011 elections, Dr Norman desperately needs to raise his profile.
There is a strong chance it will damage the Greens' relationship with Labour - as happened to the Alliance in the King Country by-election in 1998 - especially if Labour were to lose.
But for the Greens that is a "so what?" Its priority has to be advancing itself; losing the seat would have no effect on the make-up of the Government.
The Greens' decision to put up a co-leader will create a contest within a contest, against Labour for the Left.
That will cost Labour time and energy as leader Phil Goff seeks to concentrate on the bigger contest with National, over its first budget and management of the economic crisis.
The by-election will in part be a referendum on the budget, which will be delivered two weeks before the by-election, another reason for Mr Key to play down the by-election.
In an important speech, Finance Minister Bill English laid the groundwork this week for what promises to be a shocking set of figures on May 28. Using a string of eye-watering debt figures, he all but gave notice that he will have to cancel the 2010 and 2011 tax cuts if he is to have any chance of steering the debt track south instead of its present trajectory towards infinity.
And getting that arrow heading down is a non-negotiable if he is to avoid a damaging downgrade for New Zealand by the credit rating agencies.
Both Mr English and Mr Key have put so much store in preventing a downgrade that the damage of having one would be to their reputations as well as to the future cost of credit for all New Zealanders.
In the aftermath of the English speech we saw a hint of the debate that Mr Goff will mount through May and into the by-election: National reneging on the centrepiece of its election campaign, tax cuts.
Mr Goff's problem is that Labour campaigned so hard against National's tax cuts that opposing their cancellation looks confusing.
That's why Mr Goff's attack is two-pronged: focusing not only on a broken promise but the design of the tax cuts, which give nothing to low-income families.
Even then it sounds like a rerun of the election campaign, which is something Labour has been trying to avoid.
With two rounds of cuts already in people's pockets, Labour's in October and National's in April, interest rate cuts having some effect on home mortgages, and the severity of the global recession flummoxing the best and brightest in the world, National is banking on attracting no blame.
It will sell the budget and the cancelled tax cuts not as reneging but the only responsible thing to do - not culpable but responsible.
If National loses the by-election, its line will be it was always a safe Labour seat, and if it happens to win, it is a huge vote of confidence in its management of the crisis.
The dire revised forecasts in the International Monetary Fund's World Economic Outlook this week reinforces National's position that it is taking control of a situation over which it had control.
The IMF estimates that the global economy shrinking by 1.3% this year could amount to lost output worldwide of $US4 trillion ($NZ7.1 trillion) - a huge slide from its forecast in January of 0.5% growth for 2009.
Another international report, from the Organisation for Economic Co-operation and Development last week, again reinforced the Government's position that there is little room for further fiscal stimulus in New Zealand.
The constant barrage of attacks on National from Act New Zealand's Sir Roger Douglas about profligate spending dampens Labour's attacks on National as slash-and-burn merchants.
Apart from the economy, the two other big issues in the by-election will be the Waterview connection motorway (which will almost certainly be above ground) and the democracy issues in the "super-city", both of which are strong Green Party issues.
The Greens' by-election campaign could be boosted by its own budget gains - the house insulation package under its memorandum of understanding with National.
But the reality is the Greens will have almost no prospect of winning the by-election.
While third parties have done very well in past by-elections (such the Alliance in Selwyn in 1994 and Act in the Taranaki King country in 1998), they have been in circumstances where there has been a large degree of resentment over broken promises or shabby governments.
There is no comparison to the honeymoon National continues to enjoy now in its fifth month in government. It was up 0.5 to 50% in this week's Roy Morgan poll.
The Greens will simply make Phil Goff's tough job even tougher.
If finding the right issues wasn't enough, Mr Goff has caused some internal disquiet as well by forcing Mt Albert favourite Phil Twyford out of contention for the candidacy.
He also faces internal disquiet over a possible shift to the right in policy - fuelled by Clayton Cosgrove's condemnation of a Maori rehabilitative prison on separatist grounds.
That can be put on hold for the more urgent issue - holding on to what has become an iconic seat for the party.
- Audrey Young.
