This was a surprisingly good video about the math of the U.S. Electoral College system. At first I kept saying “but wait a minute…” but all my concerns were addressed in the video, and then some. I was surprised by the revelation (towards the end of the video) that it is theoretically possible (although not likely) to win the seat of President of the United States with less than 23% of the popular vote. Wow.
There is some great math of ratios and percents here. You can find data and other pertinent information about the Electoral College here.
You might also enjoy playing the Redistricting Game with your students, where you can “recast” who wins an election based on how you draw the boundaries on a map.