Great point, Peter.  It reminds me of David Brooks' observation on how the right is more invested in protecting the "covenant" (whatever the heck that means) while the left is more focused on expanding individual freedoms and identity.  Though a debatable premise, corollary to it would be the susceptibility for democrats to enhance and inflame these within party differences in the quest for identity recognition.  I do think a charismatic leader can potentially bridge these differences on the left; playing off the old political aphorism democrats fall in love, republicans fall in line.  But you're so right, we need solidarity now more than ever.