Context: The controversy surrounding the federal leadership has caused Peter Costello far more problems than anyone else in the whole fiasco. By coming out and admitting to the public that John Howard did indeed make an agreement with him to only serve 1 and a half terms before handing over to Costello has made Costello look both childish and bitter. Personally I think that the pressure on Howard to resign has lead to an intentiona politicall embarrassment of Costello. I think Howard had someone leak the information, so that Howard could then deny the accusations and get Costello back in his cage after looking like a goose in his "he said she said" press conference. It makes him look petulant and smugger than usual. His quote, "I was always told that if you've done nothing wrong you shouldn't be afraid to tell the truth" perpetuated this whole perception even further.
But was he so surprised that Howard would lie? Honestly, he hasn't really had that good a track record - right from the get go - the GST, Children Overboard, WMDs and Iraw, the IR Reforms, the AWB scandal rah rah rah...
It's pretty commonly known around the halls in Canberra that Howard's planning to step down at the end of this year, so why would Costello jump at such an obvious opportunity to make himself look like a dick. He just couldn't wait.