A color-coded map of how different states voted in the 2004 U.S. presidential election was probably the most common graphic used to convey the election results in a single picture by the news media. The following graphic by CNN uses color to highlight the states that "switched" parties.
CNN: 2004 Election Results by State
The New York Times had a more informative map that took into account population density.
"This map removes mostly uninhabited areas, revealing Mr. Bush's suburban and rural support in the East and South. "
New York Times: 2004 Election Results By County and Population
The New York Times website has an interactive feature summarizing the election results. Here is an interesting pair of graphics from this feature that explains in a single picture the distribution and results of the electoral votes.
New York Times: 2004 Election Results - Electoral Votes
Abhijeet Chavan is co-founder and co-editor-in-chief of Planetizen.