That is why there will be nothing but compassion and sympathy for Muller by his caucus colleagues and even from political rivals.
It may be catastrophic for the party. It may be humiliating for Muller. But it was not so much a brave decision as an essential one for his own well-being.
And it was better for him to recognise now that he was not built to handle pressure than to discover it in the heat of the campaign.
There is no dress rehearsal for a high-pressure job until you are actually in it.
Muller had a week from hell last week, having to cope with a full-blown scandal with only seven weeks of experience as leader under his belt and 11 weeks to go to the election.
As a leader, he made a hash of it. He should have resolved issues more quickly to force the resignation of a junior MP who abused patient information. He should have been quicker and more transparent.
The same could be said of the blatant mistruths he uttered on Thursday when answering media questions about the patient information health spokesman Michael Woodhouse had received.
He was clearly an honest man, wanting to avoid answering a question but not knowing how.
None of these added up to instances of what would be regarded in political terms as intolerable pressure.
But the events of last week were clearly the end, not the beginnings of the strains of office.
Muller quietly carried the burdens of office to breaking point. He had a tight circle of close confidantes, namely deputy Nikki Kaye and No 3 Amy Adams, and did not have a collegial style that his collegial manner would suggest.
The decisions last week appear to have been dictated and run by Kaye and Adams, not by Muller.
That ran into last weekend when he was apparently too unwell to attend the northern regional conference, and delegated Kaye to appear on the Q + A current affairs show.
The spin that Muller had been decisive compared to Jacinda Ardern's dithering over David Clark was phoney at the time and even more so in hindsight.
He was not decisive. He had difficulty making decisions. He had delegated key parts of his leadership to others and he could see it only getting worse not better.
