Treasurer Costello’s Problem

Paul Kelly has some hard questions for Peter Costello on Malcolm Turnbull and tax:

What else are backbenchers supposed to do? What conclusion about Costello will other backbenchers draw? And it is backbenchers who make and break leaders…

Is it hard in political and financial terms? Of course. But what, exactly, is Costello’s problem? Does he object to the design or the politics or just the impertinence?