But National has precious little time left to do so. The calendar might show there are still three weeks to go before election day. But if Labour goes into the final week of the campaign still enjoying the lead that it established over National in the poll then it is all over red rover.
The week prior to the Big Day is often a fizzer. The parties have fired all their policy shots. Their leaders are exhausted. Any last-minute change of tack or huge policy surprise simply invites accusations of desperation.
A big gaffe can change things - as Don Brash discovered in the final throes of the 2005 election when his contacts with the Exclusive Brethren were exposed to public scrutiny.
Ardern has suffered some so far mild discomfort regarding her stance on tax policy - and will likely continue to do so.
National will not let her wriggle off that hook. The question, however, is to what degree is she actually so ensnared.
This election is not about whether ongoing Budget surpluses make further tax cuts feasible. It is about rebuilding a decent society.
If English has made a mistake it was not saving his clever line that "hard-working New Zealanders aren't an ATM for the Labour Party" for Thursday's debate. The jibe encapsulated National's tax offensive without mentioning the word "tax". The quip needed no explanation. It was subtle. It might have floored Ardern. On such moments do such debates turn, and often the campaign and the election with them.
To have survived the first debate without too much trouble will have been a huge confidence booster for Ardern. National now has to contemplate the distinct possibility that she might go from strength to strength in the debates to come.
To add insult to injury, the detail of Thursday's poll made for very depressing reading for National's leader. It indicated that Labour and NZ First might well be in a position on election night to form a government without needing the Greens.
If such a scenario is replicated on election night, Winston Peters will not be kingmaker. He will instead have to accept he has no choice but to be part of a Labour-led governing arrangement.
To deny Labour the right to govern would be to ignore a mood for change. Propping up a fourth-term National-led administration would simply not be a goer. It would be regarded as undemocratic, perhaps even unconstitutional. It would guarantee the destruction of New Zealand First.
Even should National win more seats than Labour, Peters might well argue the winds of change are now blowing powerfully enough to warrant a change of government. Thursday may well go down in the party's history as Black Thursday.
