But then she got silly, taking the millstone that had hung around John Key's neck for eight years, promising to resign rather than increasing the pension age from 65 - doesn't she realise that we're all living and working for longer these days? It was one of those propositions put to her in the cut and thrust of debate that she may come to regret.
Just like David Lange did under the same leaders' debate spotlight in 1987 when he, on the spur of the moment, promised a referendum on MMP that he never delivered on, leaving it to others to do - a bit like raising the pension age by this Government.
We did learn a few things about what could happen following the election. On who they think would be the most attractive to Winston Peters, Ardern thought she would be because she doesn't have baggage while English just paid Peters a rare compliment saying he understood politics inside out.
And we learnt that neither would resign if they lost, hardly surprising for Ardern but unconvincing when it came to English considering he had to be talked into staying after crashing to Helen Clark in 2002.
For all his experience English seemed to find it difficult to give a straight answer when they were asked for example at the outset whether it was possible to survive politics without lying. He prattled on about earning trust and conceding that none of us is perfect.
Yep, Ardern said, she's survived politics without ever telling a lie and she assured us that was the truth.
Truth is she won the debate by a whisker.