“Democrats” is just a collective term for a group of people who tend to vote the same way and also those people who they elect.

There is no organisational structure that can decide what Democrats should or should not do.

To ask “what can Democrats do?” is a category error, similar to asking “what can Nebraskans do?”.

This gets to the heart of the failure of American politics. Power is distributed to individuals, not parties, and there is no way to get them to agree on things because there is no consequence for defection.

Ditto for Republicans.