As for what the Democrats should do, they should vote
against the supplemental. Right now they've established the worst of all worlds: they appear to have lost; they've done nothing to halt the war; they've put up a bogus bill which if they support will allow conservative Republicans to continue to screech while letting Republicans in swing districts vote for it and claim they've done something to tie the president's hands. If this is the bill, let it be a Republican bill.
