Todd Muller resigns as National Party leader

He's resigned as leader of the National Party after 53 days in the role, saying it has become untenable from a health perspective.

It's just 67 days to the general election.

Former United Future leader Peter Dunne says the intensity of the cauldron at the helm can catch people by surprise.

He says Muller had good intentions and is a decent, honest person.

However, he says the job proved to be far too much for him, given the circumstances of the moment.