A glance at the numbers in the Liberal party room goes a long way to explaining why Tony Abbott is able to affect an air of confidence regarding Tuesday's proposed spill motion.

Consider the arithmetic. With 102 parliamentarians - MPs and senators - in the room, Abbott needs 51 to join him in voting against a spill and therefore in favour of a return to business-as-usual as he cheerily put it on Saturday.

Illustration: Matt Golding.

His camp is pretty confident that right now, it has this magic number of half-plus-one, pencilled in - and a few more besides.

So why all the heat and light about the leadership? Why the talk of crisis and imminent demise? The answer lay in how those numbers add up, or more pointedly, why? And it also rests on Malcolm Turnbull not switching from passive to active mode in the next 72 hours via a frontal tilt at the leadership.