ANDREW Robb's stunning defection had been a long time coming - even if Malcolm Turnbull didn't see it before it hit him between the eyes.
Well before he quit the front bench last month to seek treatment for depression, Robb had given speech after speech slamming Labor's emissions trading scheme. He never wavered in his preference for an alternative climate scheme - one based on modelling by Frontier Economics for the Coalition and independent senator Nick Xenophon.
When Turnbull wanted to negotiate amendments to Labor's scheme in August, as the bills went to the Senate for the first time, Robb argued forcefully against. The Coalition voted no.
Around that time, some MPs floated the idea of Robb taking on a leadership role as a ''safe pair of hands'' to avoid oblivion at the next election. The putsch never eventuated. In fact, it forced Robb to confront his own demons: the depression that had hung over him like a black cloud every morning for the past 50 years.
The former federal party director knew he could never even consider a leadership role unless he could treat and beat the depression. He sought leave from the front bench to tackle it, and his leader appointed climate convert Ian Macfarlane to fill Robb's role.
Turnbull's instincts to negotiate with Labor could no longer be suppressed. He pressed for Coalition party room authority to negotiate amendments to the Labor scheme - and won. Macfarlane went to work in talks with Climate Minister Penny Wong.
During the weeks that ensued, Robb was still a player behind the scenes. His staff were seconded to the leader's office to work on the negotiation. Robb was given free access to everything by Macfarlane. He was taken into confidences.
But he was growing increasingly frustrated by the deal and how Turnbull had made it a leadership issue - forcing the Coalition to back it or cripple his leadership authority. Robb was tetchy it left no room for people like him - who back a carbon price but not the Labor model - to chart a middle course between the sceptics and the deal-makers.
He was also infuriated by how Turnbull had handled secret research he'd commissioned from Frontier, which found the Labor plan would put a $2.5 billion hole in the budget. Turnbull had shown it to Wong - but not to his own MPs. The decision to keep it from the Coalition also fed Robb's disillusionment.
In the final week, his misgivings came to a head. On Sunday night, he decided to speak out against the Coalition backing the amended scheme.
But instead of warning either Turnbull or Macfarlane, he kept his own counsel - fearing they would try to blunt his impact by bumping him down the speakers list in the party room meeting on Tuesday morning.
He also kept his plans from his staff, not wanting to compromise them.
His speech, when it came, was a bombshell. Both his leader and Macfarlane were stunned. So was everyone else in the room, friend and foe alike. One senior frontbencher described it as ''the greatest act of treachery'' they had seen in 25 years in politics. But others defended his intervention as ''courageous and principled … simply magnificent''.
But the effort of the defiance took its toll. Robb, who is still struggling with his condition and finding the experimental doses of medication variously ineffective and exhausting, was spent. He returned to his office for a kip.
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