The New York Times has the devastating report..
It begins:
President Bush was told more than a month before the attacks of Sept. 11, 2001, that supporters of Osama bin Laden planned an attack within the United States with explosives and wanted to hijack airplanes, a government official said Friday.
Read the memo for yourself:
http://www.cnn.com/2004/images/04/10/whitehouse.pdf
It doesn’t seem like a “smoking cannon” to me, actually.