The putative prime minister
Steve Lewis has taken to calling Peter Costello the putative prime minister (examples here and here).
Putative is an interesting term. According to the online Cambridge dictionary, it is an adjective meaning,
generally thought to be or to exist, whether or not this is really true:
The putative leader of the terrorist organization was arrested by police in Birmingham yesterday.
Of course, no one believes Peter Costello is the prime minister (well perhaps other than Peter Costello and Glenn Milne). Nor is putative a synonym for heir apparent or aspirational.
Consequently, I am left wondering. I am not quite sure whether Lewis is using the term sarcastically or incorrectly.