National Security: Political geography

It seems like our political landscape is unusually skewed. We are pretty much a 50-50 split nationwide. It seems every election tips the balance in one direction and then the other. The political map of the country shows something different. Most of the country is red, meaning Republican. The Democratic strongholds are much tighter, packed in metropolitan areas. A political map in color would refer to blue areas as Democratic, red as Republican and purple as a state that can flip allegiance.