“All political parties engage in criticism of their opponents”.

Easy. Don't take any notice of politicians badmouthing each other. It's not their job. Their job is to talk about Australia and what they are doing for the country: not minding the business of their opponents. It's up to electors to make decisions about politicians.

That well known political animal Joe Hockey, when part of Abbott`s team, always said that the task of the opposition was to oppose.
What a welcome change it would be if the task of the opposition was to present itself, and work towards, being a good alternative government.
No such luck I`m afraid.