In historical presidential results, many of states that went Republican ("red states") are physically large, but in most cases, their populations are relatively small. So when presidential election results are color-coded on a map of the US, it looks like red states dominate, as in this map of 2004 presidential results by state:
Even though our crazy electoral college system is "winner takes all" by state (except for Maine and Nebraska), you can get a more accurate view of how voters are distributed if you code the map by county and use red, blue, and purple colors to indicate percentages of voters:
That still looks pretty red. But if you also systematically distort the map so the drawn size of each state is proportional to its population, you get a more balanced view:
These maps are from an article by Michael Gastner, Cosma Shalizi, and Mark Newman of the University of Michigan. Read the article for other map variations and better explanations.