Politics is a numbers game. Numbers determine all sorts of things: whether a party makes it into Parliament in the first place, whether a party gets to govern, whether they're successful with legislation and in terms of this argument, whether they have the numbers to lead.
If you can't count then you should steer clear of politics.
Business leaders in a survey say National should have a leadership succession plan. They of all people should know about numbers and they should also know that in politics the idea of a successor being anointed by a leader is virtually unheard of.
Think about it, David Lange wasn't even in Parliament when Bill Rowling became Prime Minister on the death of Big Norm Kirk. And Rowling fought three elections before Lange managed the numbers to roll him. To be fair, he won more votes than National in his final two elections, but numbers in those days weren't as important, in terms of votes cast, as they are today under MMP.
There was no succession plan when Rob Muldoon clung on to power after the schnapps election in 1984. He certainly wasn't happy about being rolled by Jim McLay, which was evidenced when he was asked whether he was going to be a thorn in National's side and he said, no, he was going to be a prick.