Being called a mugwump is not a compliment. A mugwump is an individual who appears to be considering all sides of a problem at great length but is unwilling to indicate which way he or she wants to go. A political cartoononce depicted such a person as being astride a fence with his mug on one side and his wump on the other.
It was reported a few years ago that Boris Johnson, now the U.K. Prime Minister, called one of his political opponents a mutton-headed old mugwump in his Sun newspaper column. Since mugwump was more of an American term, many baffled British readers had to look that up.