[ZenGum]

We have a bi-cameral (two house) parliament.
In the lower house, there are 150 members each returned as individuals by separate districts. The ex-PM Howard was one of these. He got to be an MP by being elected by a district. Then, when his party got the majority in the lower house (thus forming government), the party elected him as PM.
The upper house has 76 members, having 12 from each state (and two from each of the minor territories), elected as a multi-member group from the whole state. These are normally elected on a party ticket - although independents can make it - and if one party member resigns or dies, the party can chose their replacement.
So I guess the idea is that if Howard were to miss out on his electorate, someone could step aside from the upper house ticket and he could slide in on that.
I don't think he'd do this. Senators are supposed to serve for 6 years and its time for Howard to retire, I can't imagine him shunting someone out to serve as opposition leader for six months, and then ... what? resigning himself and letting the first person back in? warming a bench for five years? It's time for him to walk.