I've found the idea of tribalism to be increasingly useful in understanding political behaviour. Faced with the need to make a decision based on incomplete information, people may often attempt to understand how others like them are behaving and behave in that fashion. This isn't really a new insight; politicians have been playing to group identities forever.
Perhaps this is one of the reasons I've always been so uncomfortable with tribalism, particularly in politics. It's so open to manipulation and abuse by the unscrupulous.