McMahon was way out of his depth and pretty useless but didnt seem to do anything of lasting damage.
My previous worse ever was Whitlam. As financially and administratively he was a complete numpty. But then along came Rudd and Gillard. Current list would be:
4th worse: Rudd (at least he has some intellect though no where near as much as he thinks he has)
3rd worse: McMahon
2nd worse: Whitlam
And worse by a country mile: Gillard.
As Richardson said today she avoids getting sunburnt by covering herself in excrement.