There's no doubt that National's campaign manager, Steven Joyce, thought they were in with a chance. The Prime Minister was deployed on six occasions and he, foolishly as it turned out, tried to make the by-election a referendum on Andrew Little's leadership of the Labour Party.
Just two days later Prime Minister John Key announced his resignation and his intention to leave Parliament next year.
This was a bolt from the blue.
As late as September he had been talking about a fourth term in office.
John Key, soon to be Sir John Key, is the most intuitively gifted politician this country has seen in many years and it would be entirely logical to assume that he spotted the Mt Roskill by-election result as the trigger for his sudden departure.
While I respect John Key's stated reasons for bailing out and I know from my association with Helen Clark just how gruelling the job is, John Key will know that any real election is worth a hundred polls and in real elections that his National Party has performed poorly since the 2014 general election.
The Northland by-election saw one of the safest of National electorates lost to the New Zealand First leader, Winston Peters.
National endorsed candidates like Victoria Crone running for Auckland mayor and Auckland Future, a ticket organised by former National Party president, Michelle Boag, flopped badly in the key Auckland local body elections.
Then came Mt Roskill.
Like any true professional politician (which he emphatically is), John Key knows that there are political waves that travel silently and unnoticed, like a tsunami in the open ocean. Northland, local election and Mt Roskill results suggest that just such a wave might crash ashore next year and dash his chance of a dignified retirement.
We'll see.
Key will also know that the Labour Party swamped National in the "ground campaign" in Mt Roskill.
While Labour deployed 300 activists to knock on doors, make phone calls, stuff envelopes and distribute leaflets, there was no sign whatsoever of any such effort from National.
If a party has been in government for as long as National has, a complacency develops, especially if that party has been leading in the polls.
Mr Key's successor should look hard at Steven Joyce's campaigning skills or lack thereof, and find an alternative, especially if Joyce is promoted to finance minister.
It's inevitable that deputy prime minister Bill English will again become National Party leader and therefore prime minister on Monday.
He will immediately have to confront recollections of what happened last time he did the job.
I vividly recall election night July 27, 2002 when then National Party president Michelle Boag and I represented our parties on TV1 at the historic but now abandoned Avalon Studios of Television New Zealand.
I developed an enduring respect for Michelle Boag that evening 14 years ago as National under Bill English's leadership plunged to less than 21 per cent of the party vote, by far the worst score ever achieved by any major party under the MMP system.
She didn't shed a tear.
This was the "corngate" election where a hungrier and defter opposition leader might have taken advantage of the Helen Clark Government's discomfort to make gains. This seemed beyond Bill English at that time.
It's a pity there'll be no leadership contest this time around as I personally would have enjoyed Judith Collins staying in the race.
In my role as Howard League CEO, I have met the minister and developed a positive view of the real person.
The Howard League is resolutely non-political, but I'm not.
Politics would have been sharper and much more fun with Judith Collins at the helm of the National Party.
Except for Judith Collins, the original contenders for both leader and deputy are about as exciting as the Taihape toilets.
She's at least got a bit of lead in her pencil.