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For Labour leader Ms Ardern, debate four with Ms Collins will be a bit like debate one: then, as now, she is the frontrunner and her job is to do nothing to upset that.
For National leader Judith Collins, on the other hand, nothing less than a win - and a decisive win at that - will suffice.
It may come too late, given more than 1 million people have already voted, but Ms Collins needs to win over as many wavering and undecided voters as she can before polling day on Saturday for her to have any chance of victory.
That prospect might seem remote - recent polls have National well behind Labour, which is still flirting with the hope it may receive enough votes to be able to govern alone.
However, there are various permutations of National retaining a solid core of support, Act New Zealand having a good night and other smaller parties failing to make the 5% threshold, which could result in a centre-right victory.
Ms Collins’ current strategy seems to be "scare ’em straight", with her increasingly ardent assertion that Labour and the Greens will steal your money from you through a wealth tax.
Never mind that Labour has already ruled it out and the Greens have been socially distancing themselves from their own policy - it’s now a priority worth having a conversation about, rather than a bottom line - National is going all-in on its wealth tax attack.
It is not the worst strategy the party could have come up with.
For voters deciding their party preference on the strength of how their back pocket is affected, the party promising tax cuts and arguing that the other side wants to hike taxes probably has some appeal.
National has been building "nightmare scenarios" about this tax for some weeks now, including a hypothetical Auckland pensioner in a freehold house shelling out $7000 a year in "wealth tax". Variants of that one were replayed yesterday as National released its senior citizens policy, which prominently included a no-wealth-tax pledge.
While many are entirely comfortable with the notion of paying their share in an equitable progressive taxation system, it is where the threshold in the Green’s proposal sits that plays into National’s hands.
The Greens propose a tax on anyone whose net worth is more than $1 million, as well as the introduction of new tax brackets of 37% on income over $100,000 and 42% on income over $150,000.
The party proposes that the money be redistributed to those in need through devices such as a guaranteed minimum income for the unemployed or low earners.
The Greens do make the valid point that someone has to pay for New Zealand’s Covid-19-related spending, and argue that those with the highest incomes are most able to pay a bit more.
However, with property prices at record highs and the average household income being just over $100,000, urban liberals - who are a not inconsiderable portion of the core Green vote - might well find themselves likely payers of such a tax and not be best pleased at this discovery.
In basic terms, a million is not worth what it once was.
Countries such as Norway and Italy do have wealth taxes, but a more common tax mechanism to address similar equity concerns is one that has been denied to the Greens due to Ms Ardern’s pledge never to introduce one - a capital gains tax.
National waged a war of words on that front, and is reaping similar benefits on the wealth tax front - not just from those who might be expected to pay it, but from those who aspire to one day be financially secure enough to be included in that conversation.
Whether that is enough to snare a debate win tonight, let alone an election win, is up to the voters.
Some cynically believe politicians are full of hot air ... but that can be put to good use.
National Taieri candidate Liam Kernaghan - a New Zealand champion piper - visited the Radius Fulton rest-home earlier in the campaign and promised to come back and play for the residents.
Mr Kernaghan is one politician who keeps his promises, returning recently - in full kilt, no less - to charm the voters one last time.
On the road again
New Zealand First Taieri candidate Mark Patterson has had to clock up some serious miles this election, campaigning in a sizeable seat.
Add to that several trips out of town ... the list MP was in Feilding on Monday for a policy announcement, and has made a few other excursions outside of the electorate.
Mr Patterson is not the only well-travelled southern MP this election; senior National MPs Michael Woodhouse and Jacqui Dean have also been much in demand elsewhere.