NEW YORK (AP) -- David Letterman doesn't like being stood-up -- even when it's by a presidential nominee. Republican John McCain called Letterman late yesterday, canceling his planned appearance on Letterman's "Late Show." McCain has said he was suspending his campaign to return to Washington to work on the economic crisis. But Letterman let McCain have it during most of the program. Letterman says "this doesn't smell right" and that somebody "must be putting something" in McCain's "Metamucil." But Letterman also calls McCain a true American hero. At one point during the show, Letterman had the director punch-up a live feed from CBS News, showing McCain being interviewed by Katie Couric. Letterman shouted to McCain on the screen, "You need a lift to the airport?