By releasing some of the detail of the float of shares in Mighty River Power, the Prime Minister may have finally shifted what has largely been a heavily one-sided debate on privatisation somewhat more in National's favour.
The argument is turning away from one of principle - whether minority shareholdings should be sold in the three state-owned electricity generators - to one of practicalities and the mechanics of how they should be sold.
Those parties opposing the sell-offs have had to shift the focus of their attack. Their initial target has been the "loyalty bonus" which John Key confirmed last Sunday would apply to retail investors who hang on to their shares for three years after being issued them.
As Key has pointed out, Labour and the Greens are guilty of some inconsistency. The two Opposition parties oppose the sales for fear of foreign ownership. They are now opposing the loyalty bonus - a device designed to encourage New Zealanders not to sell their shares to overseas interests.
As Labour and the Greens have it, the ratio of bonus shares to ordinary shares has to be generous if people are going to be persuaded to hang on to their ordinary shares.