Peter Costello might become the next Prime Minister of Australia. He has a slim chance, but it’s there. But the scenario does not involve him replacing Brendan Nelson as opposition leader.

Much of politics is cyclical. The decade and a half just gone was the easiest of political times for incumbents, particularly in freshly deregulated economies. Tripling house prices, low unemployment and interest rates, cheap consumer goods and a casual attitude to foreign debt meant that any political party taking power was assured an easy ride.

Canada’s Liberals (from 1993) and Labour in Britain (1997) and New Zealand (1999) all won easily with record majorities. Here in Australia there was a similar story at state level, and federally, even a mediocre politician like John Howard could clock up a few (modest) wins.

But electoral gravity gets you in the end, and now all the above national governments have either been ejected from office or look set to be.

By contrast, the 1970s oil shock and stagflation saw short governments as the norm.

So what of the current cycle? It is possible that future observers will look back on a tanking international economy and attempts to tackle climate change as resulting in a period of frequent changes of government.

A large part of politics being about luck and timing, whoever is Liberal leader in 2010 would then stand some chance of becoming Prime Minister.

But the rub for Liberal leader aspirants is in this timing. Brendan Nelson’s 10-day overseas trip suggests he has accepted he’s a goner, but whoever takes over in 2008 is likely to face at least a year of poor opinion poll results, and the nature of modern politics means they will not last to the next election.

The trick, then, is not to be the next Liberal leader, but the one after that.

Imagine this scenario: amid a sinking economy, Peter Costello is installed six months out from the next election. Similar to what the Libs attempted with Kerry Chikarovski in NSW in late 1998 - with the important difference that the public already knows Costello. Peter can not only boast of his magnificent treasurership, but also reveal his warm and cuddly side, doing the Macarena on Sunrise and discussing his love of football. Snaps of the family, Tanya on the magazine covers, and so on.

Yes, all this stuff wears thin after a few months, but by then he’s been elected PM.

That is the best chance of Peter Costello fulfilling his ambition. But organising it would obviously be very, very tricky.