clive palmer threatens to sue campbell newman, page-16

As long as Campbell said "buy", not "bribe" then I don't see that he has anything to worry about. It is a crime to offer a bribe, not one to try to buy.

It is a fact that he was a big donor to the LNP in Qld and a reasonable interpretation that when he couldn't pull strings he withdrew his support in disgust. In common language that can reasonably be described as "trying to buy". Australian idiom would also reasonably call his gross advertising spend in the WA senate "buying a seat".

I would be surprised if "common usage" which would determine how the spoken word would be interpreted by a reasonable person, is not a defence.