Ditching Gerry Brownlee and agreeing to Bill English becoming his deputy would have been a big call for John Key, National's soon-to-be-leader. But it is the right call.
As soon as English started haggling for the deputy leadership in return for not running against Key at today's special caucus meeting, the logic became inescapable.
In accepting that logic, Key has demonstrated he has a quality essential in a leader - ruthlessness.
Brownlee is the victim, but Key needed to strike a deal with the English camp for one major reason: caucus unity.
He needs English firmly inside the tent working for him rather than operating in isolation.
It is an open secret that efforts to thwart Key's leadership ambitions were coming from English's direction. A contested ballot at today's meeting would have exposed that tension to a far wider audience.
An English challenge to Brownlee for the deputy's post would have still left the impression the caucus was highly factionalised. Had Brownlee won by only a narrow margin, he would have been weakened. An English victory would have taken some of the gloss off Key's elevation, making it appear he now had a deputy he did not want.
Key needed to reach an accommodation with English for another reason. Other MPs on National's front bench apart from English harbour worries about Key's relative inexperience but abundant cockiness - and that, combined, those characteristics will trip him up sooner or later.
One senior MP last week said getting the front bench to weigh in behind his leadership would be Key's big challenge.
Getting English on board in an oversight capacity goes a long way towards dispelling those concerns.
Another driver in English becoming deputy is Key's need to harness his policy grunt in the crucial shadow finance portfolio he is vacating, rather than leave English as education spokesman, where his work is pretty much complete. That would have given English more leverage to insist he become deputy as well.
But the idea would also have attracted Key.
One of his strengths is the respect he has for Helen Clark and Michael Cullen as political foes, particularly how the former has been able to rely on the latter as her fix-it person as Deputy Prime Minister and Minister of Finance.
Key's fresh face, formidable communication skills and self-confidence will now be complemented by English's intellect, rigorous analytical skills and grasp of detail - the so-called "dream team".
In contrast, the reasons Brownlee got the deputy's job three years ago have largely evaporated.
He was a foil for Don Brash. More centrist than Brash, he was there to act as a brake on Brash's more right-wing prescription. That is no longer needed as Key is far more centrist than Brash.
National also needed Brownlee, a natural political brawler, to compensate for Brash in Parliament, where he has been a liability. Key does not need such a crutch.
Wisely, Key has ensured Brownlee still has a major say in how things are run by making him chairman of the parliamentary wing's strategy committee and also retaining him as shadow leader of the House.
Key has passed his first big test even before being anointed leader - and that is loyalties have to be sacrificed for the party's wider good.