Small "d" democratic is something done through the process of democracy. Capital "D" Democratic is something belonging to the Democrats. It's that capitalizatio

Small "d" democratic is something done through the process of democracy. Capital "D" Democratic is something belonging to the Democrats. It's that capitalization which indicates that it's a proper noun and referring to the party with that name. Without the capitalization it's not a proper noun and does not refer to the party.