"Blue Dogs" is a nickname for a gang...er...caucus of conservative Democrats in the Congress. The name is memorable and when I attempted to track down the source, I discovered that its source is unclear. It might track back to a comment made by a Republican during the 90's about using strategies which would strangle the opponent, making him therefore "blue".
Or it could be a reference to the artist George Rodrique who paints a whole gaggle of images featuring blue dogs. One member of the Blue Dog caucus apparently had Rodrique paintings in his office. It clearly is tied to the old-fashioned phrase "Yellow Dog" which is used to describe loyal Democrats who would vote for a yellow dog before any other party.
But for sure its roots seem to be Southern and that made me think of the ultimate blue dog, Huckleberry Hound. Whatever the source, it's given me the notion to put together a small gallery of comics featuring "Blue Dogs" of various kinds.