People asserting that Gillard leaked that Abbott declined the invite to attend Afghanistan have provided everything bar a shred of evidence. Gillard's ethics may not prevent her from leaking this info, but she had no reason to believe the revelation would be damaging to Abbott. Unless she believes Abbott is a complete moron all she would have expected Abbott to do is say "I declined the PM's invitation but will be visiting the troops in Afghanistan at another time." Issue closed. Even Abbott's harshest critics wouldn't have expected a response as transparently dishonest and inadequete as the one he provided. Without that ridiculous response, there's no issue.
