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SYDNEY - John Howard has considered one unpalatable election scenario: where he wins his seat but the Government loses office.
But what if it's the other way around - he loses his seat and the Government wins?
It would be an Australian political first.
The only Prime Minister to lose his seat at an election was conservative leader Stanley Bruce in 1929, and his Government was thrown out, too.
Treasurer Peter Costello might find himself Prime Minister earlier than anticipated. This may be an unlikely scenario, but stranger things have happened.
Labor's Maxine McKew needs a swing of 4.3 per cent to unseat Howard in his Sydney electorate of Bennelong.
Meanwhile, what if the predicted surge to Kevin Rudd's Labor Party occurred in the wrong seats, and the coalition won a fifth term?
Would Costello be assured of automatic elevation to the leadership he has coveted so patiently?
In the heat of the moment, in a world where opportunity waits for no man, other aspiring leaders might sense the time to strike. All bets might be off.
Of the two scenarios, Sydney University political expert Dr Rodney Smith considers the first more likely - the Government losing office but holding on to Bennelong.
But he doesn't discount scenario two: "It could happen. It would be fascinating to see how politicians responded in new circumstances."
He also floats another possibility.
"If the PM was to lose his seat while the Government won, what if the Liberals then pressured a backbencher to resign and create an immediate byelection?
"The PM could then stand in the byelection which, of course, would be in a safe Liberal seat.
"There's a grace period - I think it's three months - where you can remain Prime Minister without holding a seat in the lower house."
Smith believes a narrow coalition win, minus Howard, could create an opportunity for an ambitious MP such as Environment Minister Malcolm Turnbull. But such a challenger's chance of success could depend on who or what was blamed for the loss of the Prime Minister's seat.
"If the majority was slim, it could be in that person's interests to hold back, wait for some destabilisation and then move. He could let someone else be the person who limped on, then come in later as the hero of the hour."
- AAP