In today's Focus on Politics podcast, Deputy Political Editor Craig McCulloch delineates the nuclear destruction of Judith Collins' leadership and assesses the fallout.

"This is not our best day," - Shane Reti

In July 2020, at what seemed like National's nadir, Judith Collins took the helm and promised to rebuild the party. She was - somewhat presciently - described as the nuclear option.

This week, she leaves the job with the party in ruins, turfed out by a shell-shocked caucus after her ham-fisted attempt to take out a rival.

Listen to the full podcast

The unravelling began Wednesday - about 9.30pm - when an email dropped in reporters' inboxes.

The press release titled "Simon Bridges demoted following complaint" referenced "serious misconduct" and said Collins had been left with no option.

It caught the media and MPs off guard, and the timing and process led them to believe more was at play.

Bridges later explained he had been at a caucus function at Wellington's Premier House in early 2016 with MPs including Jacqui Dean, and made an off-colour comment about the best way to conceive a daughter.

Dean took offence and complained; Bridges was spoken to and apologised; all of it dealt with five years ago.

Collins' actions then seem a rash overreaction, an attempt to take out a former leader widely known to be plotting a comeback; a bombshell demotion that began to look to the caucus less like appropriate discipline and more like a hit job.

Read more:

How Collins crushed her own leadership

Simon Bridges: 'It was a very poor process from Judith Collins'

Collins and Bridges should consider leaving Parliament - Finlayson

Analysis: MP disputes should allow some natural justice

Voter reaction to leadership fiasco: 'The National Party are a lost soul'

Collins may be gone but New Zealand's search for a credible, viable opposition far from over

The following morning, as MPs returned to Parliament, Bridges called it desperate. Fellow National MP and brother-in-law Simon O'Connor also did not mince his words.

"I cannot work with Judith Collins as leader and I'm handing over all my portfolios this morning. I cannot and will not work with her ... there are times when the party and its values need to come to the fore and one of the reasons this party is struggling is leadership has stepped away from those values."

Just over three hours later, Judith Collins had been voted out of the leadership, …

Go to this episode on rnz.co.nz for more details