Check out this cool interactive from the Washington Post. It explains which demographic groups voted for which presidential candidate. Final election results are here.
In the FYI category (from Politix) this is what the 2012 election results would have looked like without the 15th amendment (blacks right to vote, 1870), the 19th amendment (female right to vote, 1920), and the 24th amendment (poll tax abolished, 1964).
P.S. And, yes, I understand President Obama would not be President under 1850 rules in 2008, but you get the point.