COMMENT: The most common question in politics is, "Why not me?" That's the question National MPs have spent the week asking.

A week has never seemed such a long time in politics.

Bronagh Key made her first public appearance yesterday since her husband's shock resignation as Prime Minister.

COMMENT: Much has been made of English and Bennett's polarities - man and woman, Aucklander and South Islander, quiet and loud, solo mum and family man.

Simon Bridges has withdrawn from the contest to be National's deputy leader today - handing it to Paula Bennett.

Reputation studiously rebuilt after a political mauling 14 years ago, the new PM now has chance to right the record, writes Claire Trevett.

COMMENT: As we farewell a gifted PM we are about to get a more combative one. John Key's politics have been emollient, Bill English is abrasive.

The advantage Bill English has when he forms his new Government next week is that he won't be burdened by high expectations.

Paula Bennett is a handful of votes away from becoming New Zealand's Deputy Prime Minister.

COMMENT: For a decade National didn't have to think about a leader, now they will be scrambling to make sense of it all, writes Barry Soper.

COMMENT: The stable predictable thing is English for PM, Bennett the deputy and Joyce for finance. Not my ideal, but safe. But is it enough for election year?

COMMENT: Alas, poor John, an ominous rumbling noise started in the bowels of the party's massive backbench rump. It could not be ignored.

COMMENT: 'The personal is political": a slogan that John Key, our outgoing Prime Minister, fudged vigorously throughout his tenure.

Judith Collins has laid out her policy agenda if she is elected Prime Minister.

The National Party is inviting Kiwis to thank John Key for his 10 years leading the party and eight years' service as Prime Minister.

Fevered lobbying to become the next PM has begun in the National caucus as Bill English, Judith Collins and Jonathan Coleman vie for position.

National Party politics - and, by extension, New Zealand politics - have suddenly become very uncertain.

COMMENT: I'm not gonna lie. I'm glad to see the back end of him. Clothed, of course, writes Rachel Stewart.

Leadership contests are usually damaging for political parties - but National's will be mercifully brief, writes Audrey Young.

It was the first time in Parliament since PM John Key announced he was going and Labour's front bench was a 10-metre-wide grin of schadenfreude.

National MP Nikki Kaye has returned to Parliament for the first time since her cancer diagnosis, confirming she will stand again in Auckland Central.

COMMENT: Having ticked all the boxes John Key leaves at the peak of his popularity and powers. It doesn't get any more impressive than that.

The cohesive National Party caucus that John Key has led for 10 years is about to start fraying as members grapple with how to replace him as PM.

COMMENT: If there were family reasons for John Key's decision to stand down, they were surely the demands of his art-school daughter or YouTube son.

John Key's bombshell announcement yesterday has thrown New Zealand politics into turmoil.

Labour appear quietly thrilled about the prospect of a National Party without John Key.

Key says there is no secret scandal behind his decision to resign, saying he wanted to rewrite the rule book on leadership departures and do so on his own terms.

National faced a more uncertain future without Key at the helm, says University of Auckland political scientist Raymond Miller.

COMMENT: Winning that elusive fourth term in office has just become much harder, writes Newstalk ZB's political editor Barry Soper.

His body language suggested he was speaking honestly, an expert says.