After all, Helen Clark's Labour Government introduced the Criminal Proceeds (Recovery) Act, which reverses the presumption of innocence and requires criminal suspects to prove they obtained money and assets legally, or have them confiscated by police.
National also calculated there is a part of the liberal left that would become outraged at the seeming disregard for fundamental human rights and come out swinging against National for the gangs.
There is an academically fashionable view that gangs are really community-minded groups for the dispossessed, and de facto social service providers. In a way that's true, but it's like saying McDonald's is an organisation to provide temporary accommodation for sick children.
It confuses corporate social responsibility (that is, marketing) with the true nature of the beast. Ordinary people see this clearly in a way experts and well-meaning civil rights advocates do not.
The election race is now nerve-rackingly close, even if the weight of polling gives National a slight edge. A straight run-off that pitted National against gangs and their supporters would be much easier to win.
But Labour did not take the bait. Jacinda Ardern was politely dismissive of the policy, responding that she would have to "see the detail". In part, that may be a product of her formative years in Murupara and a family in law enforcement, giving her a less-blinkered view of the social problems facing small town New Zealand than others in her party, or than National has given her credit for.
Just as importantly, Labour's refusal to be drawn into the exchange signals a major change from its losing 2008, 2011 and 2014 campaigns. The party is concentrating on promoting its own messages and not seeking the limelight by chasing National. That's in keeping with the Ardern buzzwords of "relentless positivity", but is only possible because of the party's renewed strength.
Ardern is running her own race.
So Steven Joyce returned to another old favourite, suspicions about Labour's economic credibility.
The Finance Minister's claim that Labour's projected budget had a $11.7 billion hole because of faulty mathematics has not been stacked up yet.
It appears to hinge on semantics in the way Labour's budget described some spending rather than hard figures. Grant Robertson's firm denials meant he avoided a catastrophic "show me the money" repeat of 2011's campaign, which was the equivalent of a 50-tonne Acme anvil falling on Phil Goff.
Pending genuine independent assessment, the result of yesterday's budget skirmish was a draw.
Nonetheless, Labour remains vulnerable on its future economic plans. If resisting engagement with National's populism shows discipline, Ardern and Robertson's refusal to engage on the details of their own tax policy is a risk entirely of their own making.
Ardern has described the "values" she wants from the working group which will determine Labour's tax plans, but the proposal is vanishingly insubstantial when it comes to detail such as terms of reference, priorities or the sectors from which potential members will be drawn.
It's the policy equivalent of a tunnel painted on the side of a cliff, and National will be hoping the blissfully unaffected Ardern keeps running towards it.
