Hipchadd77 said:
In the case of Kevin Rudd, he's said himself he'd do anything to win this election (and I believe him), it's likely that on some issues he is lying about his true stance and thus hasn't realised the superiority of stance Y at all.
I would say that the liberal party 'want' to be more economically right wing than they currently are, and are just kept a little closer to centre because of voters (so they don't look like 'evil capitalists'). An example here is Nick Minchin, who actually felt that WorkChoices didn't go far enough to deregulate, but just had to settle because voters wouldn't take it.
In the same way, I get the feeling the labor party want to be more economically left than they currently are, but don't want to look like a bunch of weirdo communists in comparison to the rest of Australia, so they stay centre. An example of this is Gillard, who is very left-wing afaik, but she has to make out like she cares about small business etc.
There's this perception that an 'extreme' position is somehow less valid purely because its an extreme. (eg WorkChoices had to be softened because people thought it was 'too harsh', even when the only solution that makes sense is zero labour market regulation) This kind of thing keeps politics from getting too far away from centre, although the 'centre' is moving over time too.