If the institution that exists to resolve disputes within the American center-left does not operate according to democratic principles, then I see no reason to continue participating within that institution. If that institution fails to respect democratic principles in its most important internal contest of all--nominating an individual for President of the United States--then I will quit the Democratic Party. And yes, I am perfectly serious about this. If someone is nominated for POTUS from the Democratic Party despite another candidate receiving more poplar support from Democratic primary voters and caucus goers, I will resign as local precinct captain, resign my seat on the Pennsylvania Democratic State Committee, immediately cease all fundraising for all Democrats, refuse to endorse the Democratic "nominee" for any office, and otherwise disengage from the Democratic Party through all available means of doing so.
Robert Michel's "Iron Law of Oligarchy," formulated in 1911 in reponse to his dismayed discovery that socialist parties including the German Social Democratic Party were not much different in their internal organizations and power structures from other parties:
"Who says organization, says oligarchy."
--Jacob T. Levy