Op-Ed Contributor YESTERDAY the Senate failed to reauthorize the USA Patriot Act, as a Democratic-led filibuster prevented a vote. This action - which leaves the act, key elements of which are due to expire on Dec. 31, in limbo - represents a grave potential threat to the nation's security. I support the extension of the Patriot Act for one simple reason: Americans must use every legal and constitutional tool in their arsenal to fight terrorism and protect their lives and liberties. The attacks of Sept. 11, 2001, made clear that the old rules no longer work. The terrorists who attacked...