In the past they have used bribery of various forms and triangulation to keep the group together.
In this last election cycle where the elite rigged the primary elections for Hillary and against Sanders, the Democrat elites destroyed the coalition in a way that it can not be put back together.
Republicans came close when the party elite and major donors refused to back either Trump or Cruiz hoping that a more “traditional Republican” would get the party nomination.
The Democratic Party is dead as the leaders will not surrender control to others and because without trust the coalition can never be rebuilt.
It's Democrat...
Democrat party.
There's nothing democratic about them.