Mark Schmitt wrote for the New York Times about what it means to be a Democrat:
If you’ve watched or attended past Democratic conventions, you know that the party’s coalition was stitched together from organized interest groups, and the seams start to show quickly.
They were mentioned line by line in speeches: unions, especially those for teachers and public employees; environmental groups; workers for reproductive rights, L.G.B.T. rights, civil rights and gun-control laws; campaign-finance reformers; and so forth.
Not many of these causes had universal support among elected Democrats, and keeping this coalition of interests intact was the work of the party. When Democratic leaders did their job right, as in the 1990s, this coalition held together. An ideological movement needs a steady diet of enemies and ever bigger promises, whereas interest groups are satisfied with incremental progress and a seat at the table.