its an old and historically bad joke, the media likes to make hay out of nothing, when some reporter asked in the after math of the shooting asked who was in control Of the White House because the President was down and the Vice President was out of town Secretary of State Alexander Haig stated that till the Vice President got there he, as the highest ranked member of the cabinet would be in control of the running of the White House, our sound bit media saw a story(thats what they all making some one look bad) and made it look like Haig was stating he was acting President or some such thing
from what I remember, Haig didn't mention the VP, and flat out said "I'm in charge". I was in college at the time, and can remember saying to my roommate "No he's not!"