John Howard and the leadership of the Liberal Party claim they had nothing to do with this, and it is quite possible they didn't. However, they have created a party machine where, in the past, the use of race has been a legitimate (not in my opinion, I stress) weapon to include in political warfare. I imagine most observers of previous elections would agree.
So, while the racist leaflets may not have been approved by the leadership, I can't help thinking that an example, for behaviour, tactics etc, has been established at the most senior levels and it is no surprise that it would be imitated at more junior levels, albeit, in this case, not all that junior.
True leadership would set an example to follow, not poor behviour to imitate.