They are not in panic mode yet, the MPs who could lose their jobs, but it may not take much to get them there.
However, there is an array of issues arising from the Williamson scandal that Labour could target.
The police role, for one. The police come out of it with a little credit but some discredit.
At least they stuck to their guns and pursued the charges of domestic violence against Donghua Liu in the face of inferred pressure from Williamson's phone call.
But two questions remain: why did the police actually review the case after Williamson's phone call and why did someone in the police not blow the whistle on his call?
It is evident that a culture of toadyism exists to the extent that senior officers did not recognise political interference for what it was or were willing to ignore it.
While the behaviour of the police is as disturbing as Williamson's, Labour is more likely to go for political targets such as Prime Minister John Key and Police Minister Anne Tolley rather than the police themselves. It's also likely to reignite the saga around Justice Minister Judith Collins and her dealings in China with Oravida, whose directors include her husband.
A fresh batch of papers on Oravida from the Ministry of Foreign Affairs and Trade released under the Official Information Act and further disclosures of political donations to National out yesterday will provide more oxygen.
Tolley will not be a useful target given that she was informed only on Monday by the Police Commissioner about Williamson's call.
Key will be a difficult target in terms of his precise response to events once he knew about them, but he can't escape entirely. The buck stops at the top and the mud is starting to stick. His Government and party look like they will bend over backwards to help their wealthy Chinese friends and donors.
Williamson's continued protestations that somehow it is normal for MPs to call the police on behalf of constituents in this sort of situation are compounding that reputation. If it is true, it is a disturbing state of affairs that needs immediate attention.
His claims also ignore the fact that his offending was as a minister of the Crown, not an MP.
Higher standards of behaviour are expected from ministers. Ministers form the Government, not MPs. They control Budgets and policy and people's lives.
It turns out that Williamson, at the same time as being Building and Construction Minister, was donkey deep in efforts to help this property developer well beyond supporting him for citizenship, which in itself may not have been advisable.
In the absence of ministers setting boundaries for themselves, Key may need to review the Cabinet Manual with a view to setting clearer boundaries around ministers, especially ministers acting in a supposedly non-ministerial capacity.
Can a minister really ever claim not to be a minister, or to be a minister for some purposes but not others?
The Williamson affair has not only left a stench over the Government, it has also helped Labour in eclipsing the furore over Shane Jones' departure.
It also promises to provide a major distraction from National's neatly planned build-up to the May 15 Budget.
David Parker's successful launch of Labour's new monetary policy helped in that regard, too, confronting National's narrative around the Budget.
Key and Finance Minister Bill English have so far tried to make the Budget about maintaining controls over Government spending to limit interest rate rises, which would otherwise run rampant under the ill-discipline of Labour economic management.
Labour's policy this week was all about off-setting interest rate rises.
The proposal that the independent Reserve Bank could vary employee savings rates between 8 per cent and 10 per cent as an alternative to raising the official cash rate was imaginative but not so unorthodox as to call it wacky.
Parker may have achieved a first in being able to turn monetary policy into a sound bite — "wouldn't you rather pay more into your savings account than pay extra interest to a foreign bank?" — as well as producing a 24-page backgrounder on the policy.
With some details undecided, it created debate and enhanced Parker's credibility as a finance spokesman — although the extent of change in Labour's KiwiSaver policy has been under-stated.
Its previous policy was to reduce the minimum employee contribution from 3 per cent to 2 per cent and increase the employer contribution from 3 per cent to 7 per cent. It is now more likely to be a phase-in to 6 per cent for employees and keeping employers at 3 per cent.
The success of the launch was not a fluke. It is an idea Parker has fleshed out over time with two other finance heavyweights, Sir Michael Cullen, the former Finance Minister who stays with him on his regular visits to Wellington, and Trevor Mallard, Cullen's former associate minister.
In fact, Cullen raised the idea of using compulsory KiwiSaver as a monetary policy tool back in December 2012 during discussion around Treasury's long-term fiscal report. It has had a long gestation and its messaging has been finely honed.
Labour leader David Cunliffe should feel pleased heading into the House next week but the pressure on him will be immense.
The Speaker will almost certainly grant a snap debate on Tuesday on Williamson's resignation and give Labour further opportunity to keep the Government on the back foot.
If Cunliffe and Labour cannot make the most of next week, the past week might turn out to have been the best he ever had as leader.
Debate on this article is now closed.
