[kosciusko51]

I expected all of them to have signed it as well, and was surprised to find out they did not.

[mellow velo]

I believe many of these same Democrats who were around in the mid-60s either supported the filibuster of the Civil Rights Act &/or voted against it.

So to assume they signed the Manifesto wouldn't have been a stretch. (But we all know what Felix Unger said about assume!)