The series of graphics show the election results illustrated by population, not geography.
Republicans were surprised by the win. Many had assumed—wrongly—that young people wouldn't come out as much as they did in 2008. The New York Times graph shows that not only did Obama nab young voters, but also that the numbers of young voters who voted for Obama actually increased from 2008.
While white male voters supported the Republican candidate, Mitt Romney, Obama held his support with women, increased his support with Hispanic voters, and improved young voter turnout where it mattered: in the swing states.
For serious political junkies, another graphic from the New York Times shows lots of fun facts about how voter groups since 1972 have swayed election results.
For example, Romney got the "dad" vote, while Obama secured support from voters under 30.