I watched the Capitol Limited depart Wash. Union Station this afternoon and happened to see something truly odd: the last Superliner on the consist (which was followed by the “Beech Grove”) had “For the Twenty” written in large, bold letters on the roof. I watched the train from the station parking garage, so I could not readily check the sides for any other distinguishing markings.
Ach! Found the answer to my own question. Turns out this is one of several cars used in an old presidential camapaign train. The whole slogan (over three Supes) read “Leadership for the Twenty First Century.”