Malcolm Turnbull came to the Liberal Party with ambition. He was drafted by John Howard in 2004 into the blue ribbon seat of Wentworth. In 2007, January, Turnbull was made environment minister.
Turnbull had lead the campaign of the republican movement. He had failed, but his ambition was not curbed. Howard had promised Peter Costello in the mid '90s he would transition leadership to Costello, but he had reneged, believing that it was important for Costello to seize the leadership. Costello believed a transition could be orderly, and expected Howard to step aside in his favour. Instead, Howard brought in to ministry an ambitious but highly flawed character in Malcolm Turnbull. Probably, Howard thought Costello would push aside Turnbull. Instead, Turnbull began undermining the Libs, leaking about Costello's cruelled ambition.
Following the divided Liberal Party's predictable 2007 loss, The Age canvassed leadership contenders after Costello walked. John Hewson doubted Costello was leaving, preserving a legacy of never knowing what was happening among conservatives. Hewson was a mentor to Turnbull, having had the seat of Wentworth before Turnbull. Christopher Pyne had been tasked as being a Costello supporter. In 2008, The Advertiser (South Australia based) pinned the leadership leaks on Costello in July 2006. But Costello approved them after his supporters, not named, suggested it.
In late October 2007, Turnbull acknowledged leaking to The Age on the environment policy regarding Australia not signing Kyoto. Howard reaffirmed the party policy and Costello took the view it was a mistake. The leak was important for Turnbull to put his name, unlike the leadership one, as this cast him as a rising star like Rudd on the same issue. Media were happy to not discuss what the signing of the policy would mean.
Costello had broached the issue of leadership transition in '06, it was not in his interests to keep raising it in '07. After Howard agreed to transition during the next term, the division in the party had crystallised in the public consciousness. It wasn't Costello who was leaking at that time, neither was it Howard.
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The 2007 election was lost, Howard lost his seat and Costello walked away.
