EXCLUSIVE: LETTERMAN MOCKS MCCAIN CANCELLATION Wed Sep 24 2008 17:41:58 ET David Letterman tells audience that McCain called him today to tell him he had to rush back to DC to deal with the economy. Then in the middle of the taping Dave got word that McCain was, in fact just down the street being interviewed by Katie Couric. Dave even cut over to the live video of the interview, and said, "Hey Senator, can I give you a ride home?" Earlier in the show, Dave kept saying, "You don't suspend your campaign. This doesn't smell right. This isn't the...