The political future of many MPs rests on making sure they are on the right side of any new leader and deputy leader.
In previous leadership challenges, Minister for Canterbury Earthquake Recovery Gerry Brownlee and Speaker David Carter moved up the pecking order by picking the right side.
Much depends on an early decision by Deputy Prime Minister and Finance Minister Bill English who yesterday did not rule out taking over from Mr Key.
Mr English has previously been the leader but oversaw National's worst election defeat, in 2002. While that may seem a long time ago in politics, the defeat will be used at every possible opportunity by his political opponents during next year's election campaign.
Presuming Mr English decides to run for the top job, the real nasty business for the deputy position will take place behind closed doors.
Economic Development Minister Steven Joyce, who has the nickname as Minister for Everything, will be a frontrunner to take over as deputy leader and finance minister.
Mr Joyce is National's campaign manager but as finance minister, he will be expected to campaign directly around New Zealand, not by remote control from party headquarters.
Justice Minister Amy Adams is a likely deputy.
She is from the South Island, a capable minister and was rated the politician of the year by political news sheet TransTasman.
Police Minister Judith Collins has not made any secret about her political ambitions and Transport Minister Simon Bridges has been marked as a party leader from before he entered politics. It may be a year too soon for Mr Bridges.
Climate Change Issues and Social Housing Minister Paula Bennett was a shoo-in this time last year for a top position but has not made the most of her opportunities.
After those MPs, the list is decidedly short.
From last night, MPs will have been talking about their next steps.
In contrast to Labour, where members, caucus and the trade unions have an equal say in who becomes the party leader, National leaves the decision to the caucus.
The parliamentary and party arms are separate.
Labour leader Andrew Little did not have the support of either the caucus or the party but was installed by the unions.
The National MPs will be just as ruthless as Labour but try to keep it hidden.
However, the good news for some is they have a chance to move up the rankings.
Immigration Minister Michael Woodhouse, a Dunedin list MP, will be lobbied hard by people wanting to step up to leader or deputy leader.
If he was an electorate MP, he may have negotiated some advantages for Dunedin from the ensuing lobbying.
Stranded backbench MPs and ministers outside Cabinet will also want to take their chances.
Some MPs have already announced they are leaving but others, who have languished doing not much at all will form into a powerful group senior MPs will need to deal with.
