A similar pattern emerges when gender is considered along with race. Whereas Mr. Obama enjoyed overwhelming support among black and Latino women, white women supported Romney, 56-42 percent.

In addition to non-married women, other key components of Mr. Obama's constituency were young people, racial and ethnic minorities. These are the same groups that made up much of Mr. Obama's voting block four years ago. In 2008, for instance, 66 percent of young people age 18-29 supported the president, just six percentage points more than this year. Similarly, in 2008, 95 percent of blacks supported Mr. Obama, compared to 93 percent this election cycle. This pattern is repeated among Hispanics, who in 2008 supported Mr. Obama over John McCain 67-31 percent and this year came out in even larger numbers, 69 to 30 percent.

Despite the similarities between these two elections, Mr. Obama's margin of victory this year is smaller than it was four years ago. This is due primarily the fact that while the president won independents handily in 2008 (52 percent-44 percent). This year independents supported Romney by four points, 49 percent-45 percent. A second factor which contributed to this difference, albeit to a lesser degree, is race. While whites supported McCain in overwhelming numbers (55 percent-43 percent), Romney won whites by even more -- 58 percent-40 percent.

Stanley Feldman is a professor of political science at Stonybrook University; Jeanne Zaino is a professor of political science at Iona College