Mr Howard has criticised his former deputy in his memoir.
Mr Costello responded yesterday, saying: ''It's a self-serving account in which he appears to be incapable of taking responsibility for the defeat of the government and for losing his seat of Bennelong.
''There's no point in trying to blame other people. He was the leader. He was responsible."
After Joe Hockey's attempt at showing how different he is from other shadow treasurers with his banking rhetoric, does it indicate that he is preparing for a challenge.
Not wanting to be seen as another Costello! who never did mount a challenge.
Very interesting, and even more so because all this has been prompted by Howard's book.