What, if anything, characterizes the split between the members of congress backing Clinton and those backing Obama? I think Mark Schmitt has it about right:
With the elected officials who are superdelegates now split evenly between Obama and Clinton, it seems that there are now two congressional parties, defined not by ideology but by attitude: On one side, older liberals like Ted Kennedy joined with those elected more recently who have the combativeness necessary in the Bush years; on the other side, a middle-generation elected and brought up under the assumptions of the ’80s and ’90, very roughly speaking.
Perhaps not too surprisingly, Clinton seems to be strongest among people who saw their major political ascent occur during the period of her husband’s presidency. Among both the newer cohort of Democrats, and the old-school folks who were in town long before Bill Clinton, she has less appeal. As Mark says, one interesting thing about this divide is that though it’s very heated at the moment, there’s relatively little substance to it and therefore good reason to think the congressional party will be reasonably unified irrespective of the election results. That’s a real contrast to a period when you had much deeper and more meaningful intra-party ideological divides.