Paint vs. no paint isn't the issue, it's whether Amtrak can allow a locomotive to be decorated
Why are there three engines? I'd guess for two reasons. One, the train will be traveling the SW Chief's route over Raton pass. Needs the pulling power. Second, Amtrak certainly wouldn't want one of those things breaking down and stalling the train. Gotta have backup there.
Can Amtrak carry political messages on its trains? Well, as luck would have it, I just posted this photo to my webshots page:
http://community.webshots.com/photo/109 ... 1353hjExRC
Apparently this is a leftover from President Clinton's 1996 campaign train, where a bunch of Superliners carried the message "ON THE RIGHT TRACK FOR THE TWENTY FIRST CENTURY." I guess some could argue that it doesn't specifically reference any individual candidate.
However, I have seen local transit buses in Milwaukee carry ads for candidates for mayor. I don't know if the rules differ for federal vs. local issues though.