Right Vs Left (world). Political infographic by David McCandless & Stefanie Posavec. McCandless has a great website and has produced some books on the subject.
Mid term election map
The Glaring Design Flaw In U. Election Maps: According to Lawrence Weru, purple election maps are misleading. By adding an appropriate amount of green to each blob, we can neutralize the color purple from our election maps.
Election maps are telling you big lies about small things - Washington Post
The 2016 Election Map – Medium
How to map data is a contentious debate in data visualization.
The Trouble with the Purple Election Map – Matter – Medium