Maybe I have been oblivious to it all my life, but it seems that the razor-thin and contested election in 2000 and terrorist attack the following year either created or revealed tribal identities that had gone unnoticed for a long time. Many retreated into territories defined by politics and religion. In this historic primary season it has happened again, now along racial and gender lines. It isn’t absolute by any means, just much more clearly marked. All of it is driven by group identification, and in that sense it comes from a level too low to be reached by persuasion. It may be dressed up in formal clothes, sober tones, a big vocabulary and impressive rationalizations, but much of the time what passes for dialog seems to come from some of our most primitive instincts.It seems to me what's happening falls short of a mob mentality certainly, but might rightly be called what used to be termed group think, meaning one becomes so involved in an organizational effort that it obliterates the logical filters that would ordinarily temper one's thinking.