Senator John McCain was scheduled to appear on the Late Show tonight but canceled last minute, his handlers saying he would be racing back to the capital in lieu of the financial crisis. Strangely, Letterman caught the Senator being interviewed down the street by Katie Couric. Watch what the late night anchor had to say (and watch him catching McCain in the act!) in the clip above. You can watch the juicier bits on various outlets, and the full episode tonight on CBS.