History for Snot-Nosed Leftist Bastards

I've been thinking this would be a very good time to know more about the role of the sinking of the Lusitania in bringing the United States into World War I. It could make a very good premise for a play. (The sinking of the Maine is the same kind of thing but is a better-known story, and has less ambiguity, I think.) No one says it wasn't a catastrophe--but how did it happen? Did anyone argue it was being used as a pretext? There might be an opportunity for some nice arguing.