Kerik subject to the Peter Principle

Regarding Giuliani's associate's trouble in the NYTimes article "A Defiant Kerik Vows to Battle U.S. Indictment", I thought of the Peter Principle:
"In a hierarchy every employee tends to rise to his level of incompetence."

According to the article, the highest he got in his career was being nominated for Dept of Homeland Security. It was then that his undocumented nanny got discovered, which in turn led to all the other dirt getting dug up. I've never seen such a clear illustration of the principle.