Katie Couric is on the Late Show again tonight, to try and convince David Letterman that she didn't purposely steal John McCain for her CBS Evening News that night the Republican presidential nominee infamously flaked on Letterman. Of course this is a lie, assuming Couric is as ruthlessly competitive as any network news anchor must be in order to succeed. But her exchange with Letterman is worth watching if only for all the fun bashing of Keith Olbermann, the MSNBC shouting head who filled in for McCain. Click the video icon to watch.