Republican senator vows to block nominees for national security cabinet posts until the White House "gives us an accounting" on Benghazi, the terror attack in Libya that left four Americans dead. Democrats blast the procedural hold as "unprecedented and unwarranted." Also: A debate over the Obama administration's drone wars has Republicans defending presidential prerogatives and Democrats calling for secret courts to review kill lists. Weather: New England digs out, U.S. southeast hit with destructive storms.