When former Labour MP Steve Maharey left politics, he said politicians leaving Parliament was like stepping out of a pool - the water simply came in and filled the space as if they had never been there.
What he was saying was things would carry on as they pretty much always had. Nobody was indispensable.
That got its biggest test when former Prime Minister John Key said he was stepping down last December. Sure enough, weeks later things had pretty much moved on and Key was Mr Two Per Cent in the polls.
It came to mind again this week when Labour's deputy Annette King announced she was stepping down as deputy and would leave politics after a 30 year career.
Some have blamed media for this scenario. That forgets Labour leader Andrew Little has already shown he knows his own mind.
There is more than a whiff Little had already given King a clear signal of the decision that he wanted her to make for herself.
He has dodged questions about whether he talked about it with King prior to the byelection.
He is grateful for her loyalty so Little gave King the space she needed to make 'her' decision.
He even told a few necessary fibs to give King the dignity she deserved, saying after the byelection that there was 'no vacancy' and he was not planning a change.
The fact that was all he said should have been a clue.
The last time this speculation arose, he defended King at length listing the attributes she had that made her a valuable deputy.
This time he tendered no such explanation.
King was a comfort blanket. The fact he was willing to let that go is a sign of Little's increased confidence and comfort in his role.
There are some in Labour who are fearful (and some in National who are hopeful) that Labour's caucus will become a more fractious bunch without King's tender ministrations.
It was a further step in Little's slow process up getting his dominoes in line for the election. As Baldrick would say - he has a cunning plan.
With somewhat forensic precision, he arranging things to try to squeeze out as many votes from as many corners as possible.
Ardern is responsible for doing that in Auckland, Willie Jackson among urban Maori, and Raymond Huo among Chinese voters (and donors).
Then there was the arrangement with the Greens and the recruiting of Greg O'Connor to try to get Damed Spot [Peter Dunne] out of Ohariu and Parliament.
Little has been on his own one man travelling show, speaking to increasingly decent turnouts at meetings around the country.
Things might have got messy at points but Little has shown he is capable himself of keeping a lid on disunity in caucus.
The promotion of Ardern was not Little's only move of the week.
He also decided to use the spare Opposition slot at his disposal to appoint NZ First leader Winston Peters to the Security and Intelligence Committee.
It is a wee treat to butter Peters up for potential government with Labour.
But it does more than that.
It also sends a signal that Labour will not cave in the Greens' peacenik attitude to the intelligence agencies.
It is that that kind of thing that gives National ammunition for a bit of scaremongering about a future Labour Greens government, especially at a time of international volatility.
The far more flinty approach of Peters to intelligence issues provides something of an inoculation from the Greens for Labour on the security front.
In return Little promised the Greens he would call them first on election night.
He reprised the old 'cab off the rank' terminology and declared the Greens would be "first cab off the rank."
This was apparently enough to placate the Greens, although as anyone who has experienced the new cab rank system at Wellington Airport knows, cab ranks can be messy affairs.
It is not so much where the cab is on the rank that matters as much as whether it can get you where you need to go - and how much it will charge for the privilege.
It is a meaningless feel-good gesture - and the Greens should know full well by now that getting the first phone call does not mean they will still be standing at the end of the talks.
Nor will security be the issue on which Labour will need to show it can stand its ground against the Greens.
Labour's vulnerability will be what it has always been: the economy.
Add in the Greens and the problem of persuading voters that a centre-left government can be trusted with the books becomes even more difficult.
By way of neutralising that, Little may need to look at what National is doing that warrants keeping.
A good place to start would be public service restraint if Labour wants to show it will not be profligate with the taxpayers' money.
Labour needs to show it has the strength and numbers to keep the Greens in line.
The real goal of bringing Ardern into the mix is to try to grow Labour's vote. But the risk is that it will only result in poaching from the Greens.
For a long time Labour and the Greens have simply been sharing the same share of the vote. When the Greens go up, Labour goes down and vice versa.
Since February 2014, the combined Labour - Green vote in polls has dropped by 1.5 points.
National's share has dropped even more - by about 3 points. The beneficiary of both has been NZ First.
For all his efforts, Little is yet to see a reward from Labour voters. His ratings are lower than his last two predecessors.
Labour supporters have proven to have either a very long grieving process or to be inordinately stubborn.
In the nine years since Helen Clark left the party has put up four leaders, none of which Labour voters have backed in great numbers. Contrast that with the speed with which Key's support transferred to English among National voters.
Bringing Ardern in was a gutsy move because there is a risk she will overtake Little as preferred Prime Minister.
That does not appear to have spooked him or put him off advancing Ardern, which is to his credit. He cannot afford to let his own ego get in the way.
But it will inevitably spark attempts to paint Ardern as a potential threat to Little.
That will not come from Ardern herself. Ardern has repeatedly insisted her ambitions do not lie in that direction.
From most MPs' such assurances are just meaningless white noise. From Ardern it appears to be genuine. The only other politician you can say that about is Annette King.
Ardern may well want to actually have a life that is not politics. She might want a family. She will want to wait to see what else life might have in store for her before deciding on her ultimate ambition.
Alas, poor Jacinda - within a week she has found herself with an electorate she never expected to have which was held by two former leaders as well as a deputy leadership role she didn't put her hand up for. She may find the fates are conspiring against her.