"I don't think anyone is surprised when they reflect on those facts that he's choosing to go now," Mr Hague said.
It was still a shock to see such a well-established part of the organisation go.
Mr Hague had known Dr Norman's plans for a few days but the rest of the party only found out today. It was appropriate to give the party time to absorb the news before making announcements about bids to succeed Dr Norman, he said.
It was good that Dr Norman had made his announcement early in the parliamentary term. Whoever the new successor was would have most of three years for the public to get to know them.
Mr Hague thought the party had a lot of strong potential successors. As Dr Norman had said, a new co-leader would bring different strengths and a new energy to the role.
Asked if he had previously considered the leadership, Mr Hague said it had not been an ambition.
He was in Parliament because he was "passionate about issues" and the values the Greens stood for. He now had to consider how he could "best advance those values and polices."
English-born Mr Hague, a former chief executive of the West Coast District Heath Board, became a list MP in 2008, and as a gay man he has been a staunch opponent of discrimination based on gender and sexual orientation.
The new co-leader would be male, as the party always had male and female co-leaders. He would not have to be a Parliamentarian. Any financial member of the Green Party could stand.
Dr Norman was not an MP when he was first elected as co-leader.
