Kerik is a scumbag who associates with scumbags.
In sales, that is called a "big fat claim." It is quite effective, seriously, when you follow it up with evidence.
I admit I haven't followed this very closely, but all I am aware of is the old "hiring of an illegal alien" card being played against him.
He could be dirty. I don't know. I didn't really follow this that much and had heard he was sort of a "kid from the wrong side of the tracks makes good" sort of story.
Is there a lot of compelling stuff coming out about him?