Barack Obama captured the White House on the strength of a substantial electoral shift toward the Democratic Party and by winning a number of key groups in the middle of the electorate. Overall, 39% of voters were Democrats while 32% were Republicans—a dramatic shift from 2004 when the electorate was evenly divided. The Democratic advantage in Election Day party identification was significantly larger than in either of Bill Clinton's victories.
While moderates have favored the Democratic candidate in each of the past five elections, Barack Obama gained the support of more voters in the ideological "middle" than did either John Kerry or Al Gore before him. He won at least half the votes of independents (52% vs. 49% for Kerry), suburban voters (50% vs. 47% for Kerry), Catholics (54% vs. 47% for Kerry), and other key swing groups in the electorate.
Without a doubt, the overwhelming backing of younger voters was a critical factor in Obama's victory, according to an analysis of National Election Pool exit polls that were provided by National Public Radio. Obama drew two-thirds (66%) of the vote among those younger than age 30. This age group was Kerry's strongest four years ago, but he drew a much narrower 54% majority.
Obama's expanded support did not extend to all age groups, however. In particular, McCain won the support of voters age 65 and older by a 53%-to-45% margin, slightly larger than Bush's 52%-to-47% margin four years ago. Notably, Al Gore narrowly won this age group in 2000 (50% vs. 47% for Bush).
Read the full report Inside Obama's Sweeping Victory on the Pew Research Center Web site.