Continuously attacking your opponent, especially in a Town Hall format will make him look petty. It's kind of funny how that one debate has put him in a no-win for the 2nd one; if he presses too much he looks like a jerk-but if he doesn't attack he looks like a weakling.
Obama and Biden are not centered human beings. They twist in the winds, because they have not been properly held accountable and cannot stand it when someone holds their feet to the fire. They want to blame someone or change the subject. They do not know how to handle it when challenged.