14/09/2015 5:28 PM AEST | Updated 15/07/2016 12:51 PM AEST

Turnbull Needs A Stronger Case Than 'I'm Not The Other Guy'

Alex Ellinghausen, Fairfax Media

Australian politics as we have always known it is irreparably changed.

Far from drawing a line under years of instability under two Labor Prime Ministers, the Coalition has now embraced the very 21st Century view that first-term prime ministers are fair game.

This afternoon's Prime Minister has only just passed two years into his first term. Malcolm Turnbull will be our sixth PM in just eight years and our fourth in two and a half.

There's no denying Tony Abbott's Government appeared to be dysfunctional. Cabinet leaks, bureaucratic and legislative constipation and ongoing dissatisfaction with the way his office was run have dogged Abbott since early in his term.

Talk of a spill earlier this year put the Prime Minister on notice that changes to his team were needed to make amends -- changes Abbott couldn't, or wouldn't, bring himself to make. But it can't have helped that those opposed to him have done their best to foster the perception of chaos.

And now Turnbull has finally shown his hand.

His case for taking such drastic action -- even though it's been done twice before since 2010 it is still drastic -- is not yet clear.

Yes, Abbott might be flailing, but if Turnbull is to avoid starting his Prime Ministership with the same lead weight of treachery that dogged Julia Gillard around his neck, he needs to make a stronger case for his ascension than "I'm not the other guy."

If he is to pull together a government riven by factional infighting, and get an agenda through a Senate that has so far been poorly managed by the Coalition minority, we need to know what sort of Prime Minister Malcolm Turnbull wants to be.

It's not long since Sara Ferguson's The Killing Season laid out in all its inglorious vanity the details of the bloody battle over the Prime Minister's office between Kevin Rudd and Julia Gillard.

The starkest political lesson from that period was that Gillard and her backers never recovered from knifing Rudd behind closed doors, without laying any groundwork with voters, or providing any context. Until the newly-minted PM Gillard told us Rudd had lead a government "that had lost its way", very few knew.

Rudd was still popular with voters, who were staggered to go to bed one night with him as leader and wake up in the morning to our first woman PM.

Abbott's ground was clearly more shaky -- with a disapproval rating of nearly 60 percent. But it's not a lay-down certainty that Turnbull will significantly turn things around. Among Coalition voters he is still 8 points behind Abbott. And he has to make the case that this is about more than popularity. If voters suspect the Liberals have thrown a Prime Minister overboard just because they fear the results of this weekend's Canning by-election, Turnbull will spend what little time he has before the next Federal Election fighting the perception he's just a political opportunist.

His comments this afternoon that, "there must be an end to policy-on-the-run and captain's calls" had such a familiar ring.

Australian voters must be tired. Tired of the uncertainty, tired of the vanity, and tired of turning up to the ballot box only to have their decisions overturned by a few.

This post has been updated to reflect the result of tonight's leadership ballot.