Grattan on Friday: Michelle Grattan , University of Canberra What on earth was Julie Bishop thinking when she declared she’d support a “formal investigation” into this week’s damaging cabinet leak? Bishop was defending herself as the questions swirled about who might be the leaker, saying it wasn’t her. But to have one of the most senior ministers – she’s deputy Liberal leader too - talking about a probe into cabinet members just underlines the serious breakdown not just in the government’s discipline but in its common sense as well. The leaked story was by the Daily Telegraph’s Sharri Markson, reporting that a “despondent”: cabinet had discussed, in the context of the backbench revolt on banking, whether the government should capitulate and hold a royal commission. Treasurer Scott Morrison said no; Peter Dutton, one of the conservatives who has had Malcolm Turnbull’s back, was reported to be “opposed in principle” but open to the idea on pragmatic grounds. But Turnbull remai...